lighting, light produced by artificial means to allow visibility in enclosures and at night. For stage lighting, see scene design and stage lighting.
Early Sources of Artificial Lighting
The earliest means of artificial lighting were the open fire, firebrands, and torches. The first lamp was a dish of stone (later of clay, pottery, or metal) containing vegetable or animal oil and a wick. This was succeeded by the candle, first made of wax and later also of tallow, and by the lantern, which is of early origin. The Argand burner was an improved oil lamp with a burner and a chimney, and this type of lamp was widely used after the Canadian geologist Abraham Gesner popularized the use of kerosene.
The Introduction of Gas as a Fuel
Coal gas was first used as an illuminant in the late 18th cent. by the engineer William Murdock in England and by the engineer Philippe Lebon in Paris. It was used in London in 1802, in Baltimore in 1817, and in New York state in 1823. The invention of the Bunsen burner by the German chemist Robert Wilhelm Bunsen and the invention of the Welsbach mantle, a device developed by the Austrian scientist Carl von Welsbach that gives off bright light when placed over a flame, greatly stimulated the use of gas for lighting purposes.
Electric Lighting Comes of Age
The first development in electric lighting was the arc lamp, which was evolved from the carbon-arc lamp demonstrated in 1801 by Sir Humphry Davy, in which an electric current bridges a gap between two carbon rods and forms a bright discharge called an arc. Early lamps of this type were made with an open arc; later ones were enclosed in glass and thus made more practicable. Carbon-arc street lamps, first produced by the American scientist Charles F. Brush, were used in Cleveland in 1879 and soon came into wide use in other cities. The mercury-vapor electric lamp was devised by the American inventor Peter Cooper Hewitt in 1903. This type of lamp makes use of a pool of mercury liquid in a condition of high vacuum; when an electric current passes through the mercury it produces ionized vapor, which gives off a blue-green light. Modern improvements have given this lamp a much greater efficiency. The neon lamp, developed by the French physicist Georges Claude in 1911, has been largely used in commercial signs.
The Incandescent Lamp
The incandescent electric lamp, in which an electric current passing through a resistance filament (e.g., one of carbon and tungsten) enclosed in a vacuum tube heats the filament until it glows, was developed by the American electrician Moses G. Farmer in 1858–59 but was not practicable. Sir Joseph Swan in England and Thomas Edison in the United States, working independently, developed lamps of this kind; the lamp patented by Edison in 1879 was the first widely marketed incandescent lamp and was the forerunner of the modern Mazda lamp that utilizes a filament of drawn tungsten hermetically sealed in a glass envelope. A gas-filled incandescent lamp was invented by the American chemist Irving Langmuir in 1913. In the United States, the Energy Independence and Security Act of 2007 mandated the sale of more energy-efficient incandescent (and other) lamps; the phase-in of the requirement for lamps that use 30% less energy began in 2012.
The Fluorescent Lamp
The French physicist A. E. Becquerel constructed a fluorescent lamp and described (1867) the preparation of fluorescent tubes basically similar to those made today. Considerable progress in developing fluorescent lighting was made in several European countries, and during the 1920s high-voltage fluorescent tubes were used in advertising signs. In the United States the first practical hot-cathode, low-voltage fluorescent lamp was marketed in 1938. This is the form of lamp still commonly used. It consists of a long, sealed glass tube with an electrode at each end; a small amount of mercury is contained within the tube. The inside surface of the tube is coated with a mixture of fluorescent powders. When an electric current is maintained through the lamp, the mercury becomes vaporized and gives off invisible ultraviolet radiation that is absorbed by the fluorescent coating. The coating then emits visible light. The fluorescent lamp is often easily distinguished by its tubular design—straight, circular, or bent in a U or other shape. Compact fluorescent lamps, usually designed to screw into the socket originally made for an incandescent lamp, are now also shaped to resemble the less efficient incandescent lamps that they are intended to replace.
Contemporary Lighting Technology
The search for efficient artificial lighting during the 20th cent. first focused on improving incandescent lamp technology and high-intensity discharge (HID) lamps. The tungsten-halogen lamp, often called a halogen lamp, like the other incandescent lamps uses a tungsten filament as the light source, a gas filling that includes a halogen, and a quartz bulb. The halogens help preserve the filament and prevent lamp walls from darkening as quickly as those of the other incandescent lamps by causing the tungsten that evaporates during lighting to be redeposited on the filament instead of the bulb; more light is thus available to the task or work surface.
HID is the term commonly used to designate four distinct types of lamps—mercury vapor, metal halide, high-pressure sodium, and low-pressure sodium—that actually have very little in common. The mercury vapor lamp produces light when the electrical current passes through a small amount of mercury vapor. The color rendering qualities of the mercury vapor lamp are not as good as those of incandescent and fluorescent lamps. The metal halide lamp is similar to the mercury vapor lamp, the major difference being that the metal halide lamp contains various metal halide additives in addition to mercury vapor. The efficiency of metal halide lamps is twice that of mercury vapor lamps. Some of the newer metal halide lamps provide color similar to that of incandescent lamps while others emulate daylight. The high-pressure sodium (HPS) lamp has the highest lamp efficiency of all lamps commonly used indoors. It produces a golden-white light when electricity passes through a sodium vapor. The low-pressure sodium (LPS) lamp, the most efficient of all, is used where color is not important because all colors illuminated by an LPS light source appear as tones of gray or yellow.
The most promising technology is that of the light-emitting diode (LED). A tiny semiconductor microchip, an LED consumes little power, is long lasting, and is relatively inexpensive. It produces visible or infrared light when subjected to an electric current. First demonstrated in 1962 and appearing in a commercial product in 1968, LEDs were limited to small applications until 1985, when more powerful LEDs were produced. Their major limitation was that only red and green microchips were possible. In 1993 researchers at several universities in the United States and Japan developed an LED that produced blue light, which in conjunction with the red and green chips could produce white light. This made the LED a major player in illumination technology, and LED lightbulbs that can replace incandescent and compact fluorescent ones have been developed. The discovery of organic light-emitting diodes (OLEDs), made with plastics rather than silicon and other traditional semiconductor materials, opened the door for many specialty applications under the mantle of solid-state lighting. LEDs also offer the possibility of adjustable colors, permitting the use of lighting that enhances alertness during the daytime and aids sleeping during the nighttime, or that enhances different aspects of crop growth during a plant's life cycle.
Functional Selection of Lighting
The incandescent lamp was long the basic light source, and still remains the one in most common use, though it is being superseded by compact fluorescent and LED lamps. While the least expensive to buy, it is the most expensive to own due to its low efficiency and relatively short life. The fluorescent lamp is the second most common light source. It is widely used in factories, offices, stores, and public buildings because it produces far more light for the same expenditure of electricity than do incandescent lamps. Compact fluorescent bulbs that can act as replacements for standard incandescent bulbs are sold for their long life and energy efficiency. However, to many observers the colors of objects illuminated by a fluorescent lamp often appear quite different than they would appear if the objects were illuminated by an incandescent lamp or sunlight. More efficient LED lamps that also are capable of producing a more natural light than fluorescent lamps are increasingly replacing both fluorescent and incandescent lamps, especially in commercial settings. Sodium vapor lamps are used on some highways, as are color-corrected mercury-vapor discharge lamps. Tungsten-halogen lamps are used for lighting sports arenas and stadiums, in automobile headlights, and for residential lighting. Xenon lamps are used in flash photography as well as in cinema projectors and lighthouses.
"lighting." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (September 11, 2018). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/lighting
"lighting." The Columbia Encyclopedia, 6th ed.. . Retrieved September 11, 2018 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/lighting
Modern Language Association
The Chicago Manual of Style
American Psychological Association
LIGHTING in America prior to about 1815 was provided by a variety of devices, including lamps fueled by oil derived from animal or vegetable sources, tallow or bayberry candles, and pinewood torches. The late eighteenth-century chemical revolution associated with Antoine Lavoisier included a theory of oxidation that soon stimulated dramatic improvements in both lamp design and candle composition. These included a lamp with a tubular wick and shaped glass chimney invented in the early 1780s by Aimé Argand, a student of Lavoisier, and introduced into the United States during the administration of George Washington. The Argand lamp was approximately ten times as efficient as previous oil lamps and was widely used in lighthouses, public buildings, and homes of the more affluent citizens. European chemists also isolated stearine, which was used in "snuffless candles," so called because they had self-consuming wicks. The candles became available during the 1820s and were produced on a mass scale in candle factories.
After European scientists discovered an efficient means of producing inflammable gas from coal, a new era of lighting began during the first decade of the nineteenth century. Baltimore became the first American city to employ gas streetlights in 1816, but the gaslight industry did not enter its rapid-growth phase until after 1850. Capital investment increased from less than $7 million in 1850 to approximately $150 million in 1880. The central generating station and distribution system that became standard in the gaslight industry served as a model for the electric light industry, which emerged during the last two decades of the century. Improvements such as the Welsbach mantle kept gas lighting competitive until World War I. Rural residents continued to rely on candles or oil lamps throughout most of the nineteenth century because coal gas could not be economically distributed in areas of low population density. The discovery of petroleum in Pennsylvania in 1859 soon led to the development of the simple and comparatively safe kerosine lamp, which continued as the most popular domestic light source in isolated areas in the United States until the mid-twentieth century.
Certain deficiencies of the gaslight, such as imperfect combustion and the danger of fire or explosion, made it seem vulnerable to such late nineteenth-century electric inventors as Thomas A. Edison. Two competing systems of electric lighting developed rapidly after the invention of large self-excited electric generators capable of producing great quantities of inexpensive electrical energy. The American engineer-entrepreneur Charles F. Brush developed an effective street-lighting system using electric arc lamps beginning in 1876. One of Brush's most important inventions was a device that prevented an entire series circuit of arc lamps from being disabled by the failure of a single lamp. Brush installed the first commercial central arc-light stations in 1879. Because of the early arc light's high intensity, it was primarily useful in street lighting or in large enclosures such as train stations.
Edison became the pioneer innovator of the incandescent-lighting industry, which successfully displaced the arc-light industry. Beginning in 1878, Edison intensively studied the gaslight industry and determined that he could develop an electric system that would provide equivalent illumination without some of the defects and at a competitive cost. His reputation attracted the financial backing needed to support research and development. Crucial to his success was the development of an efficient and long-lived high-resistance lamp, a lamp that would allow for the same necessary subdivision of light that had been achieved in gas lighting but not in arc lighting. Edison and his assistants at his Menlo Park, New Jersey, laboratory solved this problem by means of a carbon filament lamp in 1879.
Edison also proved skillful as a marketer. By 1882 his incandescent lamp system was in use on a commercial scale at the Pearl Street (New York City) generating station. All the components—not only the lamp but also the generator, distribution system, fuses, and meters—needed for an effective light-and-power system were in place.
The thirty-year period after 1880 was a time of intense market competition between the gaslight, arc light, and incandescent light industries and between the direct-current distribution system of Edison and the alternating-current system introduced by George Westinghouse. Each of the competing lighting systems made significant improvements during this period, but incandescent lighting with alternating-current distribution ultimately emerged as the leader. The General Electric Company, organized in 1892 by a consolidation of the Edison Company and the Thomson-Houston Company, became the dominant lamp manufacturer, followed by Westinghouse.
The formation of the General Electric Research Laboratory under Willis R. Whitney in 1900 proved to be an important event in the history of electric lighting. In this laboratory in 1910, William D. Coolidge invented a process for making ductile tungsten wire. The more durable and efficient tungsten filaments quickly supplanted the carbon filament lamp. Irving Langmuir, also a General Electric scientist, completed development of a gas-filled tungsten lamp in 1912. This lamp, which was less susceptible to blackening of the bulb than the older high-vacuum lamp, became available commercially in 1913 and was the last major improvement in the design of incandescent lamps.
Development of a new type of electric light began at General Electric in 1935. This was the low-voltage fluorescent lamp, which reached the market in 1938. The fluorescent lamp had several advantages over the incandescent lamp, including higher efficiency—early fluorescent bulbs produced more than twice as much light per watt as incandescent bulbs—and a larger surface area, which provided a more uniform source of illumination with less glare. It also required special fixtures and auxiliary elements. This lamp came into wide usage, especially in war factories during World War II, and then spread quickly into office buildings, schools, and stores. Homes proved much more reluctant to adopt fluorescent lighting, however, in part due to the more complicated fixtures they required and in part because incandescent bulbs produced much warmer colors. Following the energy crisis that began in 1973, designers made a number of breakthroughs that boosted the efficiency of fluorescent lamps, primarily by improving the "ballasts," which regulated the flow of energy through the bulb, and by developing new, even more efficient, compact fluorescent bulbs. Many businesses also used dimmers, timers, and motion detectors to reduce energy costs.
The energy crisis beginning in 1973 little affected the lighting habits of American homeowners, unlike its effects on American business. (Household energy costs account for only about 6 percent of the lighting energy used in the United States as compared to the roughly 50 percent used by commercial establishments.) Although some installed dimmers and timers and others paid closer attention to turning off unused lights, home consumption of energy for lighting remained relatively stable. Indeed, though energy-efficient lamps became increasingly available in the 1980s and 1990s, their gains were offset by new uses for lighting, particularly with the growth of out-door lighting in the 1990s.
Bright, Arthur A. The Electric-Lamp Industry: Technological Change and Economic Development from 1800 to 1947. New York: Macmillan, 1949; New York: Arnco Press, 1972.
Nye, David E. Electrifying America: Social Meanings of a New Technology, 1880–1940. Cambridge, Mass.: MIT Press, 1990.
James E.Brittain/a. r; c. w.
"Lighting." Dictionary of American History. . Encyclopedia.com. (September 11, 2018). http://www.encyclopedia.com/history/dictionaries-thesauruses-pictures-and-press-releases/lighting
"Lighting." Dictionary of American History. . Retrieved September 11, 2018 from Encyclopedia.com: http://www.encyclopedia.com/history/dictionaries-thesauruses-pictures-and-press-releases/lighting
Modern Language Association
The Chicago Manual of Style
American Psychological Association
light·ing / ˈlīting/ • n. equipment in a home, workplace, studio, theater, or street for producing light: the heartless glare of strip lighting. ∎ the arrangement or effect of lights: the lighting was very flat.
"lighting." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (September 11, 2018). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/lighting-0
"lighting." The Oxford Pocket Dictionary of Current English. . Retrieved September 11, 2018 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/lighting-0
Modern Language Association
The Chicago Manual of Style
American Psychological Association
"lighting." Oxford Dictionary of Rhymes. . Encyclopedia.com. (September 11, 2018). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/lighting
"lighting." Oxford Dictionary of Rhymes. . Retrieved September 11, 2018 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/lighting
Modern Language Association
The Chicago Manual of Style
American Psychological Association
LightingLIGHTING CREWS AND THEIR COLLABORATORS
LIGHTING TECHNOLOGY AND FILM STYLE
To begin to appreciate the ways in which lighting can shape the ways we respond to a film, consider the scene in Alfred Hitchcock's Suspicion (1941) where a young wife (Joan Fontaine) lies ailing in her bed while her mysterious newlywed husband (Cary Grant) slowly ascends the stairs to her room, advancing through a spiderweb of foreboding shadows. On a small tray he carries a glass of milk that glows with an eerie luminosity. The scene invites us to wonder whether he might be trying to poison his wife. Such mistrust assuredly does not arise from the popular actor's star image; instead, the ominous shadows cast across the set and the covert placement of a light bulb inside the glass combine to arouse unease.
Lighting has come to be an important component of cinema's visual design. It is widely recognized that in film, as elsewhere, it can create a substantial emotional impact. A primordial response to darkness and light is a deep-seated element of human psychology that filmmakers have harnessed in order to influence the ways viewers respond to narrative development. On the one hand, deep shadows can make a character seem untrustworthy or conceal a host of horrors. On the other, bright, diffused lighting can provide comfort and reassurance or create the impression of an angelic countenance. Extremely bright light can cause discomfort, though, and can even be used as a weapon, as in Rear Window (1954) and The Big Combo (1955), where it dazzles the villains and halts their advance.
Brightness is only one variable of lighting that can contribute to the effect of a scene. The choices the cinematographer makes about what kinds of lights will be used, how many there will be, and where they will be placed all require careful consideration. Moreover, color and black-and-white cinematography each allows for different lighting effects. Colored lighting can give rise to a range of subjective impressions that may be systematically used throughout a film for atmosphere, as in the moody and heavily stylized Batman (1989), or for metaphorical significance, as in Vertigo (1958) when Scottie (James Stewart) persuades Judy (Kim Novak) to transform her appearance into that of the dead Madeleine (Novak). When she emerges from her bathroom made over into Madeleine's image, she is bathed in a green light, its supernatural associations accentuating the uncanniness of the resurrection of her alter ego.
Film lighting has three main purposes. The first is clarity of image. It is important for viewers to be able to discern all the important elements in the frame. These might range from facial expressions and physical gestures to the presence of significant props. In early cinema this was the sole purpose of lighting, but around 1905 other factors came into play. Lighting's second purpose is a quest for greater realism. Films began to introduce visual schemes that suggested that the lighting came from logical sources within the world depicted. The use of "effects lighting," as it was known at the time, paved the way for the third purpose: the creation of atmosphere or emotional effect. The development of lighting technique as a significant element of mise-en-scène became an important tool for manipulating audience responses to characters and narrative events. Increasingly, a repertoire of standardized lighting techniques came to be used for particular dramatic situations and particular lighting styles came to be strongly associated with film genres.
The person responsible for the design and execution of a film's lighting is the director of photography (known in Britain, tellingly, as the "lighting cameraman"). This feat cannot be accomplished alone, however, so directors of photography, or cinematographers, need to work closely with their own support teams as well as with a range of collaborators in other departments. The cinematographer's main assistant is the gaffer, who is responsible for designing and supervising the rigging of the lights that are required to produce the effects the cinematographer desires. The gaffer is, in turn, assisted by the best boy and a range of electricians and grips who handle the often substantial array of equipment.
The range of lights used can, in themselves, require a large crew. First they must be positioned round the set, either on stands or supported overhead, a task performed by the riggers. During filming, the lights need to be operated, which may include dimming or moving them. Some types of light, such as carbon arcs, require constant monitoring by a dedicated operator. As well as the lights themselves, the lighting department uses a wide range of other apparatus that needs to be set up, monitored, and maneuvered. Flags or gobos, screens that come in a wide range of shapes and sizes, each with a different name, are used to prevent light from shining into the camera lens or onto areas of the set where shadows are required. They also may be used to help prevent microphone stands and other set equipment from casting shadows into the frame. Reflectors are widely used, especially for outdoor shooting, to redirect light in the desired direction. The different colors and substances used to make reflectors determine the type of light reflected. A choice can therefore be made between a sunlight and moonlight effect, for instance. Diffusers—translucent screens, often made of fine mesh or textured glass—are used to soften a hard light source. When shooting with artificial lights, it is possible to place a small diffuser close to the light source, but for sunlight shooting far larger screens may be needed.
Whereas gaffers and grips deal with the mechanics of delivering the lighting, its design is a product of the cinematographer's collaboration with the director. Although some directors have only a limited understanding of lighting equipment and technique, most have clear ideas of the kinds of effects they are looking for. Normally, they seek to create a particular atmosphere as part of their film's look. They also direct the movements of the actors and the camera, and the lighting must respond to each of these for reasons of visual clarity as well as compositional effect. The lighting styles of some directors can be as individually distinctive as those of top cinematographers. Josef von Sternberg (1894–1969), for instance, had very specific ideas about the way his protégé Marlene Dietrich should be lit in films such as Dishonored (1931) and Shanghai Express (1932) (both photographed by Lee Garmes [1898–1978]) and Blonde Venus (1932) and The Scarlet Empress (1934) (photographed by Bert Glennon [1893–1967]). More recently, Clint Eastwood's work as a director has been defined by unusually low-key lighting, irrespective of film genre. Like Sternberg and many other directors, Eastwood has shown a preference for repeatedly collaborating with cinematographers who are experienced in delivering his preferred visual style. His most regularly used cinematographer in the 1970s and early 1980s was Bruce Surtees (b. 1937), who was responsible for such films as The Outlaw Josey Wales (1976) and Sudden Impact (1983). Surtees's former camera operator, Jack Green (b. 1946), then continued in the same visual tradition for thirteen films including Bird (1988) and Unforgiven (1992). He, in turn, was later replaced by his former chief lighting technician, Tom Stern, who photographed Blood Work (2002), Mystic River (2003), and Million Dollar Baby (2004).
The camera operator is another crew member with whom the cinematographer must work closely. In America, the director of photography often supervises all aspects of cinematography, including the camera and its operator. In Britain there is a greater separation of roles so that the operator is more likely to take instructions from the director. Irrespective of the line of command, though, a close relationship between lighting and camera is crucial. This is partly because the lighting design and camera placement must respond to one another, but also because the film speed (the type of film stock used and the amount of light it needs to register a clear image) affects the level of light required. The exposure time (the duration that the camera aperture is open) and the lighting levels must also be in accord with one another.
Furthermore, the cinematographer must collaborate with the members of the crew who are responsible for the appearance of the people and objects that are to be lit. Early discussions between the production designer and/or art director and the cinematographer can prove immensely beneficial, although they do not always occur. Set design can have important implications for the type and number of lights that are used, and for their positioning. The presence or absence of walls and ceilings in studio sets are especially critical in determining where lights can be positioned. Sets may be designed in such a way as to conceal light sources within the frame. Alternatively, they may incorporate visible light sources, such as table lamps, that suggest a logical motivation for the lighting used. Sometimes the set design may even include cheated lighting effects, such as painted shadows.
The use of particular colors in set design, costume, and makeup may also have ramifications for lighting design. Most lights are not pure white but have a slightly colored hue, known as their "color temperature," which can change the appearance of the colors in front of them. This affects black-and-white as well as color photography, since two very different colors may photograph identically in monochrome, or else the same color may appear quite differently depending on the color of the light. For trick effects this has occasionally been used to advantage. One of the most famous instances of a special effect achieved through colored light was the transformation scene of actor Frederic March in Dr. Jekyll and Mr. Hyde (1931), which was accomplished without any cuts or in-camera trickery. Instead, the effect was obtained by painting the actor's face with colored makeup. During filming, different-colored filters were moved in front of the lights, the technique gradually revealing the dark shadowed effect of his face paint.
The juxtaposition of dark and light surfaces may also raise lighting issues, since providing the correct amount of lighting for extreme contrasts can prove difficult. White bed sheets, for instance, may "burn up" in a dazzle of reflected light. Illuminating the scene at a lower level is likely to result in the face of someone in the bed appearing underexposed. Colored linen has often proved preferable, therefore, especially when shooting in a black-and-white, a situation that requires cooperation between the cinematographer and the art department.
As well as collaborating with other members of the production crew, the director of photography will normally try to foster a close relationship with the laboratory that develops the film. Both the apparent lighting levels and the color tones can be adjusted during the process of timing (or grading, as it is known in Britain). By deciding in advance how far this potential will be exploited, the cinematographer can choose to forego difficult on-set lighting setups in favor of emulating their effects in the lab.
There has always been a reciprocal relationship between technology and film style. The development of different types of lighting equipment and the introduction of new film stocks have both expanded the range of lighting methods and effects available to the cinematographer. Many types of lighting units were first developed for nonfilmic uses, such as street lighting or searchlights. Only later was their potential for producing cinematic lighting effects explored. Although certain styles of film lighting arose in response to technologies that already existed, many other technical innovations were the result of experiments by enterprising cinematographers and gaffers. In some instances, the name of a certain lighting effect has derived from its first use in film. One example is the "obie," a small spotlight that was designed by the cinematographer Lucien Ballard (1908–1988) during the filming of The Lodger (1944) in order to conceal the facial scars of actress Merle Oberon. The history of film lighting is a complex chronicle of intersecting influences involving technological and aesthetic innovations, periods of relative stasis, and the gradual development and refinement of existing techniques.
The lighting techniques used in the early cinema of the late 1890s and the first years of the twentieth century were astonishingly primitive in comparison with those used in still photography. Filmmakers of that era did not adopt the range of artificial lighting that was already standard equipment in photographic studios and widely used by photographers to enhance the aesthetic appearance of their work. Instead, filmmakers relied almost entirely on bright daylight. For this reason, when films were not shot on location they were filmed on rooftop sets, or else in studios built with either an open air design or a glass roof. Thomas Edison's famous Black Maria studio, built in 1892, was based on a rotating structure that allowed its glass roof to be maneuvered to follow the direct sunlight. A greenhouse-like studio built by the French filmmaker Georges Méliès (1861–1938) in 1897 that featured both glazed roof and walls and a series of retractable blinds proved to be an influential model for the design of later studios. The availability of many hours of bright sunlight was so important to early filmmakers that it has often been cited as one of the reasons that the American film industry shifted its base from New York to California (although other reasons, such as the wide range of landscapes California could offer for location shooting, also were important).
The use of daylight as the main source of illumination provided visual clarity. It did not allow as many opportunities to create dramatic effects as artificial lighting did, however. Nor did it permit indoor or night-time cinematography. The first uses of artificial lighting have been traced back as far as 1896, when the pioneering German filmmaker Oskar Messter (1866–1943) opened his indoor studio in Berlin. By 1900 the Edison studio in America had begun to make regular use of artificial light to complement naturally available light. Examples of this practice can be found in Why Jones Discharged His Clerks (1900) and The Mystic Swing (1900). Although the use of artificial lighting was initially confined to replacing or augmenting sunlight in order to provide a clear image, by 1905 filmmakers had begun to explore the creative possibilities of artificial light. In spite of the fact that the technology had long been available, the potential value of harnessing it to further the aesthetic development of film style does not appear to have been recognized in the early cinema.
Two main sources of artificial light were used at this time. One source was arc lights, which produced illumination by means of an electric spark jumping between two poles of carbon. The other was mercury vapor lights, which worked in a way similar to modern fluorescent lighting tubes. These sources allowed the creation of directional lighting, meaning that a chosen area of the set could be lit more brightly than the other parts. As the practical and aesthetic benefits of electric lighting came to be accepted both in America and abroad, some producers adopted it as their primary source of lighting, and the first "dark studio" opened in Turin, Italy, in 1907.
In America, experiments with lighting effects continued, both indoors and out. A range of new techniques were discovered, although no significant technological innovations appear to have been introduced until the 1910s. The director D. W. Griffith (1875–1948) and his cameramen were particularly active in their exploration of lighting effects, which can be found in such films as Pippa Passes (1909), The Thread of Destiny (1910), and Enoch Arden (1911). The last of these is often cited as the film that introduced a significant new technique: the creation of a soft lighting effect on faces by using reflectors to redirect strong backlight. The innovation was claimed by the cameraman Billy Bitzer (1872–1944), although questions have been raised as to whether he was really the first to use this strategy. In the mid-1910s, Griffith also began to make increasing use of high contrast lighting that cast deep shadows across characters and sets. This style had emerged a few years earlier in the Danish and German cinemas. Due to its earlier use by the famous Dutch painter, it is sometimes known as Rembrandt lighting, a term attributed to the Hollywood director Cecil B. DeMille (1881–1959), who used the technique in films such as The Warrens of Virginia (1915) and The Cheat (1915).
During the latter half of the 1910s, filmmakers adopted two significant new techniques, both derived from other art forms. One was the use of carbon arc spotlights, which had previously been used in theater and which allowed a strong light to be directed from a distance onto a particular actor or area of the set. The other was the use of diffusing screens, which already belonged to the repertoire of the still photographer. Diffusers could be used to transform a hard light into a soft light that did not cast such severe shadows. The increasing use of soft lighting techniques, whether they relied on reflectors or diffusers, had particular benefits for facial lighting. Soft lighting produced more flattering effects and, with the rise of the star system during this decade, it was becoming ever more important to make the actors look attractive.
The range of lighting sources that were used in film, and a growing appreciation of their potential to create specific effects, encouraged the development of more sophisticated lighting styles. It became common to use a combination of several lights to create a pleasing aesthetic that flattered the appearance of the actors and the sets as well as serving the film's narrative requirements. One of the best known lighting setups is the so-called three-point system, which was used primarily for figure lighting. The brightest of the three lights was the "key" light, which was directed toward the actor's face from the front-side. If this light were used on its own it would leave one side of the face in virtual darkness and cause the actor's nose to cast a large, unflattering shadow. To prevent this from happening, a second softer light known as the "filler" light was directed at the other side of the face. This light was normally positioned close to the camera, on the opposite side from the key light. It helped to balance the composition, reducing the dark shadows cast by the key light while preserving the facial sculpting. A third "backlight" was positioned behind the actor in order to create a halo of light around the hair. This served to separate the actor from the background and also helped to emphasize the fairness of blonde hair, which did not otherwise show up well on the monochromatic film stock that was used until the late 1920s.
A third type of light that came to be used in conjunction with the arc and mercury vapor lights was the incandescent light, which used a glowing metal filament, much like most modern domestic lighting. The cinematographer Lee Garmes (1898–1978) claimed to have used this type of light as early as 1919, although its first use is more commonly identified in Erich von Stroheim's Greed (1924), which was photographed by Ben Reynolds (c. 1891–1967) and William Daniels (1901–1970). Whatever the case, it was not until the introduction of panchromatic film stock in 1926 that it came into common use, when it was found that the color temperature of incandescents, or "inkies," was better matched to this stock than was that of the arc lights. Studios were quick to embrace the benefits of incandescents, as these lights required less electrical power and less manpower than other forms of electrical lighting. It was widely predicted that their use could halve the cost of film lighting as well as significantly reduce the amount of time spent in setting up and operating lights during the film shoot. A further decisive factor in the wide adoption of incandescent lights was the temporary abandonment of arc lighting with the coming of sound. Filmmakers discovered that the humming noise emitted by arc lights was picked up by recording equipment. Only in the early 1930s, after a way was found to silence them, were arcs reintroduced as a supplement to the incandescents that had taken their place as standard studio equipment.
The wide range of easily governed incandescent spotlights introduced in the 1930s allowed an ever more precise control of lighting effects. Complex systems were designed to ensure that every detail of the image was carefully governed. In his 1949 textbook, Painting with Light, the Hollywood cinematographer John Alton (1901–1996) described an eight-point system for close-up lighting (p. 99). It was based on the three-point system described above but included some extra lights that helped to improve the aesthetic effect. Three were directed at the actors: an "eyelight," which brought out a sparkle in the actors' eyes; a "clothes light," which showed up the details of their costumes; and a "kicker light," which added further definition to their hair and cheekbones and was normally positioned between the backlight and the filler light. Additionally, a "fill light" provided diffused lighting for the entire set while a "background light" illuminated the set behind the actors.
Around 1947 a new lighting aesthetic was introduced that had arisen in response to the techniques used for shooting newsreels during World War II. Shooting combat footage did not allow filmmakers any opportunities to create complicated lighting setups; instead, they had to rely on daylight, or else on a handful of powerful lights that provided a general illumination. The photofloods first introduced in 1940 were ideal for this purpose. Some fictional films began to emulate this rough and ready aesthetic. A wave of documentary-like thrillers ensued, which eschewed such complicated schemes as the eight-point lighting system in the service of greater realism. Many of these, such as Boomerang (1947) and Call Northside 777 (1948), were based on real events and filmed on location.
The 1950s saw a further erosion of the dominance of the lighting techniques that had characterized films of the 1930s and 1940s. One reason for this was the growing popularity of color filmmaking. The range of different hues meant that fewer lights were needed to differentiate between one surface and another. The backlight, which had been used to separate figures from the background plane, passed into near redundancy for a time. It still had other uses, though, one of which was to illuminate rainfall, far more visible when lit from the rear than when lit frontally. Some of the other changes in lighting technique during the 1950s can be attributed to the rapid expansion of television production. Television relied heavily on the use of live, multi-camera shooting on a studio stage. The lighting style that best suited this mode of production was one that offered a bright, even illumination of the whole set. Even though theatrical films continued to light shots with greater individual care than did TV productions, the high-key style associated with television became a widely accepted norm.
b. Johann Altmann, Sopron, Hungary, 5 October 1901, d. 2 June 1996
Regarded as one of Hollywood's most eminent cinematographers, John Alton is best known for his work in film noir during the 1940s and 1950s. His contribution to more than a dozen noirs helped to define their characteristic style of high-contrast black-and-white photography. Alton was also responsible for some very fine work in color, and he received an Oscar® for the ballet sequence of the lavish musical An American in Paris (1951). His enduring reputation was cemented further by the publication of his classic textbook Painting with Light in 1949, the first book on lighting technique by a Hollywood professional and still one of the most revealing and readable.
Alton's work is characterized by a tendency to use as few lights as possible, an approach that allowed him to create arresting images both quickly and cheaply. The speed with which he worked and his refusal to follow in the established traditions of lighting technique reportedly made him extremely unpopular with other cinematographers and lighting crew members. Nevertheless, his economical working practices and the innovative effects he achieved made him the cinematographer of choice for such renowned directors as Anthony Mann, Vincente Minnelli, Richard Brooks, and Allan Dwan.
John Alton entered the film industry as an MGM lab technician and soon became a cameraman, working for some years in Europe and then in Argentina before returning to Hollywood. The film that first propelled him to the status of an A-list cinematographer was T-Men (1947), although he had previously racked up well over forty credits. T-Men was the first of his six collaborations with Mann, which would later include Raw Deal (1948) and Border Incident (1949). While it is considered one of the first "documentary-style" noirs, at times Alton's highly stylized lighting aesthetic anticipates his most famous work: The Big Combo (1955).
Like most of the films on which he worked, The Big Combo was a low-budget affair whose apparent production values were greatly elevated by the accomplished lighting technique. Alton's sparse lighting sources sometimes bathed faces in light against backdrops of blackness, or else concealed them in deep shadow. In the final shot, now seen as one of noir's most iconic images, he silhouetted the characters against a dazzling white haze. In this scene, as elsewhere, the set dressing is virtually insignificant since the players act out their parts in a world delimited by little other than darkness and light. For the seventeen-minute ballet sequence of An American in Paris Alton used some of the same techniques including silhouetting and deep shadows. These effects were sometimes used to draw attention away from cuts, producing dramatic results. Throughout the sequence, the rapid shifts between different lighting effects and colors within a single shot are dazzling.
T-Men (1947), Raw Deal (1948), He Walked by Night (1948), An American in Paris (1951), The Big Combo (1955), Visions of Light: The Art of Cinematography (1992)
Alton, John. Painting with Light. Berkeley: University of California Press, 1995. Originally published in 1949. The 1995 edition includes a detailed introduction by Todd McCarthy.
In the 1960s and 1970s further changes in the dominant lighting styles of American cinema derived their main influences from trends in European filmmaking. The films of the French New Wave and, in particular, the work of the cinematographer Raoul Coutard (b. 1924), proved especially influential. Coutard first used his trademark technique of "bounced light" when photographing Jean-Luc Godard's Le Petit Soldat (1963). It entailed directing photoflood lights toward the ceilings of interiors so that a bright, even light was reflected down onto the scene. This technique came to be widely emulated. A contrasting trend of the late 1960s and 1970s saw many color films adopt a darker, more low-key style than had been used in earlier years. This aesthetic was integral to the somber and pessimistic tone of the narratives that flourished in this era, and Bruce Surtees's work for Eastwood can be seen to typify this vogue.
The most significant change of the late twentieth century was the introduction of HMI (hydrargyum medium arc-length iodide) lights. The HMI was a form of arc lamp that was centered on halogen gas enclosed within quartz and that had the same color temperature as sunlight. After some initial unreliability was solved, HMIs became increasingly popular throughout the 1980s. They remain one of the most popular forms of film lighting today, for both indoor and outdoor cinematography, as they are easy to use and consume relatively little power for the amount of light they produce.
At the beginning of the twenty-first century, the advent of digital cinema began to have a significant impact on the lighting requirements for certain types of filmmaking. While most theatrical features continue to be produced on 35mm film, which requires far higher levels of light than does the human eye, digital cameras are able to produce a clear image with a very low level of available light. This facility has proved especially popular with documentary filmmakers, as even indoor scenes can now be shot without additional lights. For compositional purposes, supplementary lighting is often preferred, however. Digital filmmaking using available light also has gained favor with filmmakers wishing to adopt a documentary style in the service of enhanced realism, as in the case of Michael Winterbottom's 9 Songs (2004), a digital feature that was shot entirely on location using only available light.
Fashion in lighting style has varied considerably over the years. Nevertheless, in spite of this historical variation, certain conventions concerning lighting styles have developed.
In Painting with Light, John Alton identified three main lighting aesthetics that he designated "comedy," "drama," and "mystery." Comedies, he argued, should be brightly lit with low contrasts in order to create an overall mood of gaiety; dramas should vary their lighting schemes according to the tonalities of the narrative situation; while mystery lighting, used in thrillers and horror films, is characterized by a low-key approach that swathes much of the set in deep shadow. Countless films confirm the dominance of this way of thinking, from the cheerfully illuminated comedies, Way Out West (1937) and Les vacances de Monsieur Hulot (Monsieur Hulot's Holiday, 1953), to the moody chiaroscuro of horror movies like The Black Cat (1934) and La Maschera del demonio (Black Sunday, 1960). The continued relevance of this model is borne out by a project at the University of Central Florida where researchers in the Department of Computer Science have made significant headway in developing a computer system to identify film genres in contemporary American cinema. The programmers used lighting as one of the four formal criteria by which to differentiate genres (the others being color variance, average shot length, and the level of movement within the frame). Such a measurable relationship between lighting and different kinds of narrative shows the extent to which filmmakers have adopted lighting as an important narrational tool, and emphasizes the fundamental role that lighting plays in shaping the experience of films.
Higham, Charles. Hollywood Cameramen: Sources of Light. Bloomington: University of Illinois Press, 1970.
LoBrutto, Vincent. Principal Photography: Interviews with Feature Film Cinematographers. Westport, CT: Praeger, 1999.
Lowell, Ross. Matters of Light and Depth: Creating Memorable Images for Video, Film, and Stills through Lighting. Philadelphia: Broad Street Press, 1992.
Malkiewicz, Kris. Film Lighting: Talks with Hollywood's Cinematographers and Gaffers. New York: Prenctice-Hall, 1986.
Rasheed, Z., Y. Sheikh, and M. Shah, "On the Use of Computable Features for Film Classification." IEEE Transactions on Circuit and Systems for Video Technology 15, no. 1 (2005).
Salt, Barry, Film Style and Technology: History and Analysis. 2nd ed. London: Starword, 1992. Original edition published in 1983.
"Lighting." Schirmer Encyclopedia of Film. . Encyclopedia.com. (September 11, 2018). http://www.encyclopedia.com/arts/encyclopedias-almanacs-transcripts-and-maps/lighting
"Lighting." Schirmer Encyclopedia of Film. . Retrieved September 11, 2018 from Encyclopedia.com: http://www.encyclopedia.com/arts/encyclopedias-almanacs-transcripts-and-maps/lighting
Modern Language Association
The Chicago Manual of Style
American Psychological Association
NAICS: 33-5110 Electric Lamp Bulb and Parts Manufacturing, 33-5121 Residential Electric Lighting Fixture Manufacturing, 33-5122 Nonresidential Electric Lighting Fixture Manufacturing, 33-5129 Lighting Equipment Manufacturing, not elsewhere classified
SIC: 3641 Electric Lamps, 3645 Residential Lighting Fixtures, 3646 Commercial Lighting Fixtures, 3648 Lighting Equipment, not elsewhere classified
NAICS-Based Product Codes: 33-51101, 33-51103, 33-5110W, 33-51211, 33-51214, 33-5121W, 33-51221, 33-51222, 33-5122W, 33-51291, 33-512941, 33-51294Y
Modern lighting systems are classified by the device that converts electric power into light, thus by the technology behind the bulb or the tube. The three major product groupings are incandescent lighting, represented by the ordinary household light bulb, plasma lighting, represented by fluorescent lights, and LEDs (light-emitting diodes), semiconductor light sources still in development. The category is also known as solid state lighting.
Incandescent lighting is produced by a filament made of tungsten, a metal. The filament is mounted as a connector between the two poles of an electric circuit. Current enters the filament at one end and leaves at the other through a wire. Tungsten does not conduct electricity well. It resists the current's flow. This resistance produces a very high temperature—approximately 4,600° Fahrenheit and higher. A small portion of the electrical force, maximally 10 percent, turns into light; the rest is released as heat. Tungsten has the highest melting point of all elemental metals (6,192° Fahrenheit) and the second highest melting point of all elements; only carbon has a higher melting point. Tungsten is thus an ideal filament as it can be formed into a very thin wire and heated to a very high temperature while keeping its shape. The longer the filament the more power the lamp can produce; the higher the melting point, the more light the filament will emit. In a 60 watt bulb the filament, if unwound, would be more than six feet in length. To put that much wire into a small bulb, it has to be coiled tightly and the coils coiled in turn.
In the production process, the manufacturer draws all the air out of the bulb or replaces it with an inert gas. An argon-nitrogen mixture is typical. Vacuum bulbs are used for lower wattage lamps (40 watts and under); higher wattage bulbs are filled with gas. Tiny portions of the super-heated filament boil away at high temperature while the bulb is on. In vacuum bulbs these particles deposit on the glass, at its thick end if it is screwed in upside down, at its neck if it is installed in an upright position. Over time the glass darkens and the filament grows thinner—until at last it breaks. When it does, the electric power produces a temporary arc, sometimes an audible pop, and the bulb dies. The clouded appearance of burned-out bulbs is produced by the dying arc. Producers introduced inert gas fillings to prolong filament life. The heated gas inside the enclosed bulb creates a convection current. Heated air rises, cooler air falls, hence a current. The current carries the tiny particles of filament and will deposit some of them back on the filament again so that fewer particles end up on the glass.
The most efficient incandescent lamp is the halogen lamp developed by General Electric in 1959. It did not become widely available until later. This lamp features a hard, quartz glass tube filled with inert gases with a small amount of halogen gas (bromine or iodine). Quartz glass is used because it can withstand the high heat to which the glowing filament may bring it, maximally 1,652° Fahrenheit. In a halogen lamp tungsten boiling off will form a compound, tungsten bromide; the compound will circulate in the gas. This volatilized metal is most likely to redeposit again onto the filament at those points where it is hottest—precisely those points where it is also thinnest. At the point of redeposit, the tungsten separates from the bromine, the bromine returning to the current. This technology provides long filament life but at the cost of very hot operations, limiting the deployment of halogen lights. They are widely used in automotive lighting.
Plasma or Arc Lights
The role that the tungsten filament plays in incandescent bulbs is taken over either by mercury or sodium in these lights. Sodium suggests salt, but the element is actually an alkali metal. These metals cannot be formed into a wire and are present in the glass tube as vapors suspended in the carrier, an inert gas. The two electric poles, positive and negative, are far apart—unlike in incandescent bulbs where they are physically linked by the filament. When the light is turned on, electrons come from the cathode and seek to reach the far-away anode of the circuit, traveling through the gas. In effect an arc is set up between the poles. Many electrons moving in the tube energize the gas, turning it into a plasma, thus into a mass of ionized gas, meaning a gas with many free electrons—hence the name plasma light. As the electrons speed through the tube, they collide with molecules of mercury or sodium and cause these to be excited. Excitement means that an incoming electron from the cathode causes one of the mercury molecules' (or sodium molecules') electrons to jump from its normal orbit into a higher orbit. This unstable situation soon causes the metal's electron to drop back down to its ordinary orbit, but as it does so, it releases the energy that kicked it upward—as a photon. This transaction—the leap into a higher orbit, the drop back, the release of a photon—is the source of light in every kind of lighting. In plasma lights mercury or sodium are the important actors.
Plasma lights using mercury, of which the most common is the ordinary fluorescent light, all produce ultraviolet (UV) light, invisible to humans. To serve a useful purpose, UV light must be converted to visible light. This is accomplished by coating the glass tubes of the lamp with a substance called phosphor. The material is made of rare earth elements, sixteen metals in the periodic table. Phosphor is not phosphorus although the latter's name has been appropriated because it is the element that naturally glows. Phosphor is capable of reacting with UV light and transforming most of it into visible light, the rest into heat (infrared radiation). Thus invisible light coming off mercury is rendered as visible light by means of the phosphor coating. Mercury lights are very efficient because most of the incoming energy is converted to light, very little to heat, but the frequency of this light is toward the shorter waves (green-blue) thus producing less color. This phenomenon is covered in more detail later.
Sodium-based lamps produce visible light directly but also in a very narrow frequency range (yellow-orange) so that objects of other colors appears as shades of grey. Such light is referred to as monochromatic. Sodium lamps are coated with indium tin oxide which permits visible light to exit but infrared radiation (heat) to be reflected back. Sodium lamps are the most efficient sources of light, but the monochromatic light is unsuitable for normal lighting in a home.
In fluorescent lights electric current moves between separated poles in an arc. Neural gas facilitates the movement of electrons from atom to atom across the tube's length. Electrical current flowing from the outlet comes in at 120 volts and is not suitable to start the light up or to maintain it as it runs. To start the lamp, thus to seed the interior of the tube with electrons, low power, known as cathode voltage, is needed at the coils, the latter usually made of tungsten. Cathode voltage is 20 volts. To get such power requires reducing line voltage. To produce the arc itself once the lamp has been started requires 200 volts or higher, calling for increasing the line voltage. The ballast used in fluorescent lights is the transformer that does both jobs. The older form, known as magnetic ballast, does the job with coils of wire and magnets. The advanced electronic ballast uses solid state (silicon) circuits to achieve the same end. Electronic ballasts can also modulate the frequency of the current and can thus reduce the flickering associated with conventional fluorescent light. Advanced ballasts are used in the type of compact fluorescent lights (CFLs) that can be screwed into lamps like incandescent bulbs.
Modern three-way lamps can produce light at three intensities. They have two filaments which combine to produce three levels of brightness. One, for example, will have a 30 and a 70 watt filament. When both are on they produce 100 watts. Alternatively a lamp with a 50 and a 100 watt filament will produce three levels of light at 50, 100, and 150 watts. A switch inside the lamp determines which filament should be turned on for the two lower settings and when to turn on both to get the maximum amount of light. Touch lamps feature switching activated by sensing the temperature of the finger touching the lamp. Body temperature is almost always higher than the ambient temperature in which the lamp rests. Alternatively, such lamps can detect the electrical capacitance of the skin (the electric force it stores) and contrast it to the capacitance of the lamp's surface. Dimmer switches dole out current from the electric line to the device to be dimmed, thus reducing the voltage that reaches the bulb. Dimmer switches for fluorescent lights do not work on incandescent lights—or vice versa. Fluorescent dimmers depend on the type of ballast used and must be chosen for compatibility. Some fluorescent lights will not work with any dimmer switch. Dimming halogen lights reduces the power that reaches them, thus also the heat they generate. Dimming such lights defeats their purpose, which is to increase filament life while keeping the glass clear of tungsten deposits—both dependent on heat.
The newcomer to lighting is the light-emitting diode or LED. It emerged in the 1990s and is still in early stages. A diode is a kind of valve that permits current to flow in one direction only through what is known as a p-n junction, where p stands for positive and n for negative. The junction is where p and n meet; in that gap energized electrons move around, meaning that they increase or decrease in energy. Spots where an electron was but is no longer are referred to as electron holes. When another electron encounters such a hole, it drops into it, releasing a photon. LEDs thus work very similarly to fluorescent lights. Photons are emitted through a phosphor coating converting UV radiation into visible light. LED lights have reached a luminous efficiency better than any incandescent lamp but below that of fluorescent lamps, but the technology is still young.
The color output of lamps is measured by the Color Rendering Index (CRI) maintained by the International Commission on Illumination. CRI values range from 0 to 100, in which a CRI of 0 means pure monochromatic, black and white lighting and a CRI of 100 is equivalent to color as seen in sunlight. Incandescent bulbs produce a CRI of 100, ordinary fluorescents a CRI of 63 (faces look paler), and low pressure sodium lamps used in street lights produce a CRI of nearly 0 (in its yellow-orange light people and objects are mostly in shades of gray). Our eyes are able to see only a very narrow band of the electromagnetic radiation, those with waves between 0.4 to 0.7 microns (millionth of a meter). In increasing wave lengths the colors are violet, indigo, blue, green, yellow, orange, and red. Thus the greater the wavelength the warmer the color.
The color of a photon depends on its level of energy, and that level is dependent on the distance by which the electron, displaced from its natural orbit, has jumped. In a superheated tungsten filament, all kinds of photons within the visible range of light are produced—as well as photons in the invisible infrared range. In effect the tungsten emits maximally 10 percent of its input energy as light (all colors), the rest as heat. The desirable color-rendering of incandescents also makes such lamps the least efficient. Looked at objectively, the common bulb might be described as a heater that incidentally produces light in that its function is to give light, it is inefficient.
In a fluorescent lamp, by contrast, molecules of mercury vapor are not, in effect, tortured by massive flows of current, as the tungsten filament is. Instead a single electron in the arc collides with a single electron of the mercury floating in the pressurized argon gas. When the mercury's electron drops back to is normal orbit, it also gives up a photon, but it is almost always in a narrow slice of the UV frequency. The light output therefore is unlike sunlight, which is our standard for real light. The same circumstances limit the light produced by sodium lamps to a narrow range of visible light.
Residential lighting accounts for approximately one-third and all other kinds—commercial, institutional, and industrial lighting—for two-thirds of all energy consumed in lighting. The residential segment is the dominant consumer of incandescent lighting and although, to be sure, fluorescent lights are present in many home shops, compact fluorescents are penetrating the market slowly, and LED lamps are appearing in the home, principally as flashlights.
The commercial market—using that designation, as does the U.S. Department of Energy (DOE), to refer to all other sectors—relies principally on fluorescent lighting. About three quarters of all lighting provided in nonresidential structures is fluorescent, thus making fluorescents the largest category of lighting. Fluorescent lights are the most cost-effective in terms of electrical consumption over the life of the bulb and they produce reasonably decent white light. Since this sector also includes hotels, motels, and communal living facilities, the sector is also a user of incandescent lighting, which is more pleasing to people.
Outdoor lighting uses mercury vapor, metal halide, and sodium lamps, all part of the plasma lighting category. The color rendering of these lights is inferior to fluorescent lamps but they are very efficient, have much longer life, and lowest overall costs. All of them require noticeably long periods to reach full luminosity, ranging from 2 minutes after turn-on for metal halide lamps to as much as 15 minutes for low pressure sodium lamps. It takes time to create the necessary plasma ionization before the arc that produces the light can take hold. Mercury vapor and high pressure sodium lamps are used in street lighting, metal halide lamps are favored for lighting stadia and warehouses. Low pressure sodium lamps are used in parking lots, warehouses, and tunnels. The difference between high and low pressure sodium lights is visible in their color; high pressure sodium lamps provide a whiter light because they contain mercury alongside sodium; low pressure sodium lamps produce a yellow light.
Most automobiles are equipped with halogen incandescent bulbs. Some feature so-called high intensity discharge (HID) lamps, usually with metal halide implementations working at high pressure and high heat to vaporize the metals used to produce light in a wider range of frequencies than mercury or sodium can deliver. The HIDs used in autos have rapid turn-on features, unlike larger metal halide lamps that need a warm-up.
Lamp Efficiency and Economics
The light production from a lamp is measured in lumens, one lumen being the light thrown by a candle on a square foot of surface located one foot from the candle. The efficiency of a lamp can be measured by the watts of electricity it takes to produce the same illumination. Let us assume we wish to have 1,800 lumens, the high end of an incandescent 100 watt bulb. The same illumination can be produced by a 70 watt halogen lamp and a 50 watt compact fluorescent.
According to the DOE's Energy Information Administration, electrical power cost 9.86 cents per kilowatt hour (a thousand watts) in 2006. To operate for 750 hours, the incandescent bulb will consume 75, the halogen 52.5 and the CFL 37.5 kilowatt hours—the numbers derived by multiplying 750 by the watt rating and divid-ing by 1,000 to obtain kilowatts. These numbers, times the average cost of electricity, produce operating costs of $7.40, $5.18, and $5.04 respectively for the three types of bulbs. To this operating cost we must add the acquisition cost of the bulb itself.
|Type of Lamp||Lumens per Watt||Rated Life Hours|
|Low||High||Rank Efficiency||Low||High||Rank Life Hours|
|LED stands for light emitting diode.|
|n/s stands for not shown.|
|The ranking by Life Hours has two types of lamps ranked as second as they have the same life expectancy.|
|Sodium, low pressure||183||200||1||18,000||n/s||3|
|Sodium, high pressure||150||150||2||20,000||24,000||2|
An operating time of 750 hours was chosen for this example because an incandescent lamp has a minimum life of that length. That bulb will cost $0.50, the halogen lamp $7.00, the CFL $7.50. It would thus seem that the incandescent provides the best cost-efficiency if the bulb cost must be amortized over 750 hours. In actuality, however, the halogen bulb will have a minimum life of 3,000 hours and the CFL 8,000 hours. For 750 hours, the halogen lamp itself will cost only $1.75 ($7 × (750/3,000)). Using the same approach, the CFL lamp will only cost $0.70 in the first 750 hours. Total costs therefore will be $7.90 for the incandescent, $6.93 for the halogen, and $5.74 for the CFL bulb. The CFL comes out as the winner.
Lamp efficiency is usually stated as lumen production per watt of electricity—a measure we inverted above to derive an economic comparison. Figure 123 shows the efficiency ranges of different types of lights, along with rated life hours, showing the minimum and maximum values in both categories and a ranking in each. The lamps are arranged by minimum efficiency.
Low pressure sodium lights are the most energy efficient and also have the third-highest rated bulb life. LEDs have the longest life at 35,000 hours. Incandescent bulbs come in last in both energy efficiency and in rated life. In this product category however, as in many others, sheer technical effectiveness and cost-benefit do not adequately capture the reality of the product. If we were to arrange this table by color-rendering index, incandescent bulbs would be the best (at 100 CRI) and low-pressure sodium lamps the worst (at around 0 CRI); the other categories would also stay in the same places but in reverse order. In residential settings color matters and thus trumps efficiency and cost.
The resource consequences of lumen efficiency can also be calculated for each type of light from the data in Figure 123. The theoretical maximum lumen-yield of a watt of electricity is 683 lumens per watt—although that light will be monochromatic. The energy efficiency of different lamps can be calculated by dividing lumens per watt by 683 and multiplying that number by 100 to obtain energy efficiency as a percentage. The low pressure sodium lamp, for example, with 183 lumens per watt produces an efficiency of 26.8 percent, meaning that nearly 27 percent of the incoming electrical energy is translated into light, 63 percent lost as heat. At the lowest end of efficiency, an incandescent bulb producing 10 lumens per watt, the efficiency is 1.5 percent, with nearly all incoming power leaving as heat.
The lighting sector in the U.S. economy, as it is presented by the U.S. Census Bureau, consists of four industries. Of these Electric Lamp Bulb and Parts Manufacturing provides the core product and three other industries manufacture the fixtures intended to hold the light-producing element and often also the ballast of fluorescent lights. The Census Bureau divides the field into residential and nonresidential light fixtures and into another category it labels Lighting Equipment Manufacturing not elsewhere classified. This last industry classifies outdoor lighting as one major component and flashlights and other nonresidential portable lights as the other—thus the largest and the smallest fixtures are combined in one industry.
To get some perspective on the role of each user sector, data from the DOE are illuminating. In order of importance, and measured in total electricity consumed in lighting, the top sector is commercial (51%) followed by residential (27%), industrial (14%), and stationary outdoor lighting (8%). The nonresidential sector, therefore, excluding outdoor lighting, is 65 percent of all electrical consumption for lighting.
The sector taken as a whole represented a market, at the production level, of $12.1 billion in 2005, down slightly from a level of $12.3 billion in 1997. The lighting sector as a whole is a mature industry. Looking at component industries, there is more variability seen in performance. Lamp sales have been declining at the steepest rate (3.8% per year). Sales of residential fixtures increased at a nominal 0.9 percent per year, essentially flat. Commercial, industrial, and institutional fixture sales declined at 1.4 percent per year. Outdoor and portable lighting showed the only growth, roughly matching that of durable goods in the economy, increasing at 3.8 percent per year. The performance of the sector's component industries is shown graphically in Figure 124.
Despite continuing innovation in lighting, the technological thrust has been to produce more efficient and particularly longer-lasting light bulbs. These more efficient and longer-lasting devices have much higher prices but provide substantial savings in use. The feedback to residential consumers, however, works rather poorly. Bulbs represent a tiny portion of total household spending. In order to realize how high the savings are, people would have to keep track of bulb life and make extensive calculations to determine the level of energy savings they have achieved. Most consumers do not bother. Acceptance of high-priced bulbs is therefore slow. Competition, however, is intense. Market research firms who follow these products, Mintel International Group Ltd. being an example, thus conclude that the light bulb market has traditionally low growth. Competition causes prices to fall. Acceptance of new products leads to lower replacement rates. As a consequence unit sales to satisfy a given rate of demand decline with bulb efficiency. Demand is largely a function of household formations, which have been advancing at the rate of 1.4 percent per year in the 1997 to 2005 period.
Within the residential market, fixed light fixtures, thus ceiling- or counter-mounted devices, representing 59 percent of the market in 2005, exhibited positive growth at 3.5 percent per year—yet slower than new housing completions in the same period of 4.1 percent yearly. The other categories of residential lighting, however, namely portable devices, have been declining at a rate of 4.7 percent per year. The reason for this decline may be loss of earning power and a busier lifestyle, which impacts home decorating projects.
Within the commercial/institutional/industrial sector, only industrial lighting fixtures (representing just under 19% of the market) exhibited growth at 5.2 percent per year. Other users have purchased fixtures at declining rates of nearly 4 percent per year. The sharp dip in fixture consumption in this sector beginning in 2001 and lasting until 2003 was most likely the consequence of the recession that began in 2001, putting the brakes on corporate expenditures.
Outdoor and portable lighting (excluding lamps in the home but including flashlights) have shown a contrary pattern, quite possibly mirroring a sense of insecurity in the public in the aftermath of terror attacks and other dramatic incidents of public violence, such as massacres at schools. This category exhibited largely flat performance in the 1998 to 2001 period, as shown in Figure 124. Sales rose sharply between 2001 and 2002 and have been climb-ing since. Outdoor lighting grew at 1 percent in the 1998 to 2001 period but at the rate of 2 percent in the 2001 to 2005 period. Flashlight sales declined in the 1998 to 2001 period at nearly 3 percent per year and grew at a heady 11 percent yearly between 2001 and 2005.
The top producers of lamps in the United States are General Electric, Osram Sylvania Inc., Philips Lighting Company, and Feit Electric Company, Inc., thus a publicly held U.S. corporation, a German multinational, a Dutch multinational, and a privately held U.S. company.
Thomas Edison formed General Electric Company (GE) in 1890 as the umbrella organization for various enterprises. Edison was one of the inventors of the incandescent lamp. He filed his patents for the device in 1879, a year after the British inventor Joseph Wilson Swan obtained his patent for a similar device Swan had first introduced in 1860. Edison did not succeed in defending his patents in the United States, where the U.S. Patent Office declined to recognize his design, saying that it relied on the earlier invention of another pioneer, William Sawyer. Edison also could not prevail in Britain, but he produced his own invention, which was superior to others, under contractual agreements and thus launched an industry. GE has gone far beyond light bulbs in its lengthy history. In its official filings with the Securities and Exchange Commission for 2006 (in the company's 10-K report) GE reported sales of $163.4 billion. Of that total its industrial segment accounted for 20.5 percent of revenues. Lighting products barely received a mention at the tail end of a discussion of a sub-segment, Commercial & Industrial Products. Nevertheless, General Electric had the dominant market share in light bulbs and tubes in the United States in 2006, holding in excess of 70 percent of the market.
Osram Sylvania Inc.
This company is fully owned by Osram GMBH, headquartered in Munich, Germany. Osram, with 2006 revenues of €4.6 billion, is part of Siemens. Approximately 43 percent of Osram's sales were realized in the Americas, much of the total by Osram Sylvania. In the period 1909 to 1993, Sylvania, which began as Hygrade Incandescent Lamp Company in Salem, Massachusetts, operated as a manufacturer of light bulbs and other electrical products. Sylvania's founder began his career by buying burned out light bulbs, removing their filaments, and producing new bulbs from old. Between 1959 and 1993 Sylvania was owned by General Telephone & Electronics (GTE). Osram purchased GTE's lighting operation in 1993. Osram Sylvania has a market share of approximately 8 percent in the United States.
Philips Lighting Company
Part of Royal Philips Electronics, Philips Lighting Company is based in The Netherlands. That global company reported €27 billion in revenues in 2006 of which lighting products represented €5.5 billion. Approximately 29 percent of the company's revenues were earned in North America. The company's U.S. share of the lamp market was approximately 4 percent.
Feit Electric Company, Inc.
This company is a privately held bulb producer headquartered in Pico Rivera, California. Feit began operations in 1978 as a manufacturer of fluorescent lamps. Its own brand of products commands a 1 percent share of the lamp market. Feit is also involved in substantial private label lamp production for others.
Light fixture manufacturing is an extremely fragmented market with many small participants. In the Census Bureau's 2002 Economic Census, 1,092 companies were reported to be participants in the industry. These companies operated 1,155 establishments of which 699 had fewer than 20 employees. The market is thus populated by many small producers domestically. In addition, valuable lamps—chandeliers, for instance—are imported predominantly from Europe.
Cooper Lighting Industries Ltd.
This company, based in Peachtree City, Georgia, is representative of the handful of diversified and large producers of lighting. Cooper grew by acquisition of lamp companies and had sales in 2005 of $4 billion. Cooper combines the capabilities of nine separate companies, including Halo Lighting and McGraw Edison, the latter having acquired Halo.
Acuity Brands, Inc.
This company is a publicly traded diversified fixtures producer with 2006 sales of $2.4 billion, of which 72 percent were realized in a wide line of lighting fixtures serving industrial, commercial, institutional, municipal, and residential markets. The balance of Acuity's products were chemicals.
Two other large participants in the market in 2006 were Hubble Lighting, Inc., with electric fixtures representing $1.6 billion of its total sales of $2.4 billion in that year, and Genlyte Group Inc., which had 2006 sales of $1.48 billion. Genlyte concentrates on light fixtures for a wide market.
MATERIALS & SUPPLY CHAIN LOGISTICS
If there is a critical material consumed in lighting, it is tungsten. The metal is used, although in different ways, in all kinds of lamps except LEDs, although in somewhat different ways. Tungsten wire is the second highest material input to the lamp and bulb manufacturing industry, glass holding the top rank as an input. The United States no longer has active tungsten mining operations although reviving closed mines was under discussion in the latter half of the first decade of the twenty-first century. Producers obtain the metal from scrap and from imports, principally from Canada. The world's largest producer, with the largest reserves of the metal, is China. China accounted for 84.6 percent of world mine production and 62 percent of world reserves in 2006 according to the U.S. Geological Survey. China's own consumption of tungsten, however, has increased significantly so that the country was actually importing tungsten scrap to alleviate local shortages there. Canada, with 9 percent of world reserves, is the closest source of tungsten for U.S. producers. More than half of all tungsten is used as an alloying agent to harden other metals in critical wear applications; tungsten production in machinery applications, therefore, drives the demand, not lighting.
Glass bulbs and tubes are manufactured in so-called ribbon machines, originally invented by Corning Glassworks. Molten glass runs on conveyor belts equipped with tiny openings through which glass is blown by machine into molds to produce blanks in various sizes and configurations. These high-precision, high temperature operations are centrally located and feed lamp producers pre-coated blanks ready for assembly. This portion of lamp production is part of the Pressed and Blown Glass and Glassware Manufacturing industry (NAICS 32-7212) centered in Ohio, New York, Pennsylvania, West Virginia, and South Carolina.
In the lighting fixture segments of the industry a great diversity of semi-finished materials are fabricated and purchased components are assembled into fixtures of all kinds ranging from small flashlights on up to street lights resting high on poles made of aluminum and steel tubing. Apart from the residential sector in which the single most important input, as measured in dollars, is paperboard packaging material for shipments of relatively small items, the largest input to lighting fixtures are specialty transformers and fluorescent ballast manufactured by electronics components producers in industries upstream, as it were, from fixture manufacturers. Specialty transformers and ballasts were also the second highest inputs for residential fixture manufacturers.
Lamp and bulb production in the United States is concentrated in Connecticut, Illinois, California, and New Jersey, the states shown in rank order based on shipments in 2002. Lighting fixture production is much more widespread. The top producing states, in order of 2002 shipments, were California, Illinois, Pennsylvania, New Jersey, Ohio, and New York, thus concentration matches population densities across the country.
Lighting plays so universal a role in human affairs that distribution of lighting products takes place through multiple channels. Landscape and garden lighting fixtures, for example, may be found in garden centers, endoscopes for lighting the interior of the body are delivered by the medical supply chain, auto lights (and their replacements) are sold through automotive dealerships, municipalities and highway departments purchase outdoor lighting systems by public procurement, and the list could be extended to many more niche markets.
Residential bulbs are sold through hardware stores, drug stores, food stores, department stores, and mass merchandisers. Low-end fixtures are typically also available in such outlets. Higher end fixed lights and portable lamps are sold in furniture stores and specialized lamp stores. These channels are supplied by distributors who, in turn, rely on electrical or specialized lighting wholesalers.
Specialized lighting distributors play an important role in servicing builders and contractors who work on behalf of commercial, industrial, and institutional clients. These wholesalers typically offer very extensive lines of lighting fixtures, systems, and components ranging from interior to outdoor products. Some wholesalers are further specialized to serve important lighting markets such as theatrical and movie lighting applications.
In that all people need lighting—even the sightless do so on behalf of those close to them—we are all key users. The context of lighting, however, the places to be illuminated and for what purpose—creates quite different user profiles. Residential and similar lighting (hotels, resorts) is dominated by incandescent lamps because a full range of colors is important to simulate daylight. Lighting fixtures, similarly, are used as means of expressing aesthetic values. In more practical situations where lighting becomes a functional means to an end, economic efficiency becomes the crucial element. Fluorescent lighting is a good compromise in that it produces good lighting at low cost at the sacrifice of CRI. Outdoor lighting of streets, buildings, and parking lots to prevent accidents or to discourage crime require minimum color rendering but consume high amounts of energy. It is costly to light the night when confining walls are absent and do not help by reflecting the light back. These applications use the most cost-effective sources of light with the least pleasing appearance.
Mood lighting provided by candles represents the closest adjacent market to utilitarian electric light. Rare indeed is the household where candles affixed to candlesticks are entirely missing and where, on festive occasions, the lights are not dimmed and shadowy but smiling faces are lit by flickering but very warm lights, and candle flames reflect from raised glasses.
Gas lights used in outdoor lighting represent an alternative. Such lighting is used both in residential and municipal settings to provide a traditional feel to certain areas. Oil lamps are used in camping situations and when the lights fail.
In that lighting is a central aspect of decoration, all interior furnishings, from carpets to drapes to wall coverings, from furniture to paintings to sculptures to knick-knacks, are adjacent markets when lighting is chosen to illuminate such surroundings and, sometimes, new lighting installations lead to changes in furnishings.
RESEARCH & DEVELOPMENT
The central focus of R&D in lighting is on solid state lighting (SSL) based on light-emitting diode technology. In describing its programs of R&D support for this technology, the Department of Energy states: "No other lighting technology offers the Department and our nation so much potential to save energy and enhance the quality of our building environments." LEDs have emerged as a technology capable of providing very high efficiencies in converting energy into light (rather than heat) while providing a superior CRI approaching, and eventually matching, that of incandescent bulbs.
DOE expends approximately $1.3 billion annually supporting research on building efficiencies. Of that a portion is dedicated to supporting lighting innovations by sponsoring research by universities, corporations, associations, and national laboratories. An example of such research was the development of an organic light-emitting diode lamp by Universal Display Corporation producing light at 45 lumens per watt, matching fluorescent lamps, but with a CRI of 78 (versus 63 for fluorescents). The efficiency and color production of such lights is expected to improve; they already have the longest lamp life on record, and their performance is not affected, like all other lights are, either by vibration or by on-and-off switching. In just the LED category alone, in 2007 DOE was supporting 43 projects, and sponsoring others with GE, Philips, and Osram Sylvania. These companies were financially participating in the sponsored research with R&D expenditures of their own.
DOE is also sponsoring research intended to improve conventional lighting processes, focusing attention on higher-efficiency filaments for incandescent lamps, next-generation fluorescent products, and multi-photon phosphor research. The last category represents basic research on phosphors used to coat fluorescent lights with the aim of doubling their output of visible light and producing an ideal multi-colored spectrum of light.
R&D in this field is aimed at major improvements in lighting efficiency on the one hand, promised by the exploitation of semiconductor technology, the aim being energy conservation, hence DOE's participation. On the other hand, the aim is to improve the color-rendering index of efficient light sources to aid their acceptance by the public.
Perhaps the two most important issues impacting lighting are global warming, viewed as, at least in part, human-caused by emission of carbon dioxide, and looming future shortages of petroleum and, in due time, all other hydrocarbon fuels as global resources are drawn down. Efficient lighting is one way to reduce carbon emissions and to conserve fuels.
Public efforts to forcibly cause the population to conserve energy used in lighting have surfaced in the latter years of the first decade of the twenty-first century. As reported by Diane Katz in Michigan Science in August 2007, "the incandescent light bulb no longer will be sold in Australia, Canada, Cuba or Venezuela within five years. Similar phase-outs are pending in California, New Jersey and several other states as well as the European Union."
Such legislative efforts are matched, as already noted by extensive and in part publicly-supported activity to provide the consumer with products that deliver the same warm light in a new package, eventually at the same low acquisition price.
TARGET MARKETS & SEGMENTATION
The subdivision of the market into major user segments with different requirements has been noted at various points above. Under this heading we need only to note in addition that lighting products must be sold not only to their ultimate end-use consumers but also to at least two professional categories that importantly influence what kind of products are purchased: architects and engineers. Producers in the industry therefore expend marketing and sales efforts to reach these professions in efforts to keep them abreast of new developments.
RELATED ASSOCIATIONS & ORGANIZATIONS
The Illuminating Engineering Society of North America, http://www.iesna.org
International Association of Lighting Designers, http://www.iald.org
National Electrical Manufacturers Association, http://www.nema.org/about
"The Arc Lamp." Industrial Electronic Engineers, Inc. An IEE Archives Department Exhibition. Available from 〈http://archives.iee.org/about/Arclamps/arclamps.htm.〉.
Darnay, Arsen J. and Joyce P. Simkin. Manufacturing & Distribution USA, 4th ed. Thomson Gale, 2006, Volume 2, 1387-1397.
"Did Thomas Edison Really Invent the Light Bulb?" Demand Entertainment, Inc. Available from 〈http://www.coolquiz.com/trivia/explain/docs/edison.asp〉.
"Fluorescent Lighting." HyperPhysics. Available from 〈http://hyperphysics.phy-astr.gsu.edu/hbase/electric/lighting.html〉.
Goodman, Marty. "History of Electric Lighting Technology." Available from 〈http://www.sheldonbrown.com/marty_light_hist.html〉.
Katz, Diane S. "Fluorescent Revolution." Michigan Science. August 2007.
Lazich, Robert S. Market Share Reporter 2007. Thomson Gale, 2007, Volume 1, 1863.
"Light Bulbs—US." Mintel International Group Ltd. Available from 〈http://www.mindbranch.com/listing/product/R560-700.html〉.
"Lighting Research and Development." Building Technologies Program. U.S. Department of Energy. 30 August 2006. Available from 〈http://www.eere.energy.gov/buildings/tech/lighting〉.
"Measuring Light Source Life." Building Technologies Program. U.S. Department of Energy. Available from 〈http://www.netl.doe.gov/ssl/usingLeds/general_illumination_life_measuring.htm〉.
"Product Summary: 2002." 2002 Economic Census. U.S. Department of Commerce, Bureau of the Census. March 2006.
"Tungsten." Mineral Commodity Summaries. U.S. Department of the Interior, Geological Survey. January 2007.
"Value of Product Shipments: 2005." Annual Survey of Manufactures: 2005. U.S. Department of Commerce, Bureau of the Census. November 2006.
"Lighting." Encyclopedia of Products & Industries - Manufacturing. . Encyclopedia.com. (September 11, 2018). http://www.encyclopedia.com/manufacturing/encyclopedias-almanacs-transcripts-and-maps/lighting
"Lighting." Encyclopedia of Products & Industries - Manufacturing. . Retrieved September 11, 2018 from Encyclopedia.com: http://www.encyclopedia.com/manufacturing/encyclopedias-almanacs-transcripts-and-maps/lighting
Modern Language Association
The Chicago Manual of Style
American Psychological Association
Light is essential for human life. Modern societies have created homes, schools, and workplaces that rely on electric light sources. Some of the electricity used to generate the light in these spaces is wasted, largely owing to ignorance. The efficient application of electric, as well as natural, light sources to the human condition is a sophisticated effort, but one that is essential to a sustainable and enjoyable future.
WHAT IS LIGHT?
Humans are a diurnal species, which means that we are active in the day and asleep at night. Indeed, daylight is the primary stimulus to the photobiological system that regulates our sleep-awake cycle. Of course, while we are awake, we see, and we depend a great deal on seeing. Approximately 80 percent of the human brain devoted to sensing the environment is devoted to vision. It is not surprising, then, that from the beginning of human history we have strived to produce and control light.
Until very recent human history, the Sun had been our primary source of light for both seeing and waking. Over the past two millennia, and particularly over the past two centuries, our direct reliance on the Sun for light has diminished. Today it can be argued that large segments of affluent human societies are exposed to light from the Sun only rarely. Many people spend virtually all of their active lives under manufactured light sources of various types.
These manufactured light sources are, perhaps ironically, largely dependent on the Sun. The radiant energy from the Sun has been stored in the fossilized remains of billions of creatures over millions of years and is used to power the electric light sources created by modern humans. The power generated by hydroelectric sources also is a result of solar evaporation and subsequent rainfall. Only nuclear reactors provide power independent of the Sun, which is, of course, the largest nuclear reactor in the solar system.
Ironically, too, without humans there cannot be "light." In other words, we formally define light in human terms. Radiation from the Sun and from other sources varies in frequency. These different frequencies have been categorized for convenience into different bands. The highest frequencies are in a band known as cosmic rays, and the lowest are in the radio frequency band. Between these two extremes is a very small band of radiant energy known as visible radiation, or light. Only radiation in the narrow region of the electromagnetic spectrum visible to humans can be called light. All other radiation, even that seen by other species outside this band, cannot technically be referred to as light. We measure the frequency of radiation within the visible band in terms of wavelength. By convention, the visible band ranges from 380 to 780 nanometers; one nanometer is one billionth (10-9) of a meter.
Photoreceptors in the eyes convert radiation in the visible band into neural signals that reach the brain. Photoreceptors are located throughout the retina, a sensory membrane that covers the entire back of the human eye, as shown in Figure 1. One eye contains approximately 130 million photoreceptors. We have, however, two distinct classes of photoreceptors, rods and cones. Rods are more sensitive to light and are used primarily for nighttime vision, whereas cones, of which there are three types, are used for daytime vision. These two classes of photoreceptors enable human vision to comfortably span light levels from a sunny, snow-capped mountain to faint starlight, a billion-to-one range. The three cone types provide us with the ability to convert light into color. Indeed, color is not an inherent property of light. Rather, the human brain "calculates" color from the neural signals generated by the three cone types.
MEASUREMENT OF LIGHT AND COLOR
Light is measured in several ways. Until about 1960, most light measurements were obtained by visual comparison. A standard light source of known, but adjustable, brightness was compared by a trained technician to another light source of unknown, but fixed, brightness. When the two lamps were seen to be equally bright, they were said to produce the same amount of light. Naturally, this technique was fraught with problems of inconsistency and inconvenience. Today photosensitive electronic detectors are used to measure light accurately and reliably. They convert radiant energy into a measurable electrical signal that can be used to quantify the amount of light generated by a source.
The measurement of light is known as photometry. (Color measurement is known as colorimetry; see below.) Photometry can be performed in several different ways, depending on the geometric relationship between a light source and a detector. Most light measurements are based on the flux (photon) density on a detector. This quantity is known as illuminance and represents the rate of photon absorption by a detector of known area. From an illuminance measurement other photometric quantities can be derived. Flux, measured in lumens, is simply the total amount of light generated by a source. Intensity, measured in candelas (cd), is the amount of light projected in a given direction and within a two-dimensional (solid) angle. Luminance, measured in candelas per square meter, is comparable to the human perception of brightness because it accounts for both the amount of light reaching a surface and the amount of light reflected from that surface back to the eye. For many years luminance was known as photometric brightness, but this term is no longer used.
Photometric measurements do not weight all wavelengths in the visible band equally. Rather, a specific weighting function for the electromagnetic spectrum is employed to define "light" (see Figure 2). This function, known as the photopic luminous efficiency function, is not based on the responses of all of the photoreceptors in the eyes. Rather, it is based on the spectral sensitivity of only two cone types found only in the small region of the retina known as the fovea. Responses by the photoreceptors in the fovea enable us to read and see fine detail, but they represent only about 4 percent of all the photoreceptors in the retina. The photopic luminous efficiency function was established by international agreement in 1924 and has been used as the standard weighting function for light ever since.
Light also can be defined in other ways, even though these definitions are rarely used. For example, the scotopic luminous efficiency function was established in 1951 by international agreement to represent the spectral sensitivity of rods (see Figure 2). This function is rarely if ever used in photometry because the presence of almost any light source, including moonlight, will raise light levels to a point where some cones also function for vision.
Light sources vary in their ability to produce light—that is, to produce radiation within the photopic luminous efficiency function. In general the efficiency of extracting energy from fossil fuels or other energy sources and converting it into light is very low. For example, the efficiency of light extraction by an open gas flame is only about 0.04 percent. Not until very recently, with the advent of electric light sources, was it possible to substantially increase extraction efficiency. The conversion efficiency of the most efficacious electric light source presently manufactured (low-pressure sodium) is, however, only about 30 percent.
All electric light source efficacies are measured in terms of their ability to generate light per unit electric power, measured in lumens per watt (lm/W). However, efficacy is only one consideration in selecting a light source. For example, the most efficacious light source, low-pressure sodium, essentially produces a single wavelength of light (589 nanometers), making every object color appear as different shades of yellow. For some human activities the absence of color information is not important, but for others it is not only unpleasant but also dangerous (e.g., in surgery). It is beyond the scope of this article to compare light source cost, maintenance, safety, flexibility, and operating conditions, but all of these factors, not just efficacy, are extremely important in selecting the right light source for a particular application.
However, two points about energy efficiency need to be stressed. First, power and energy are two different quantities, and second, high light source efficacy (lm/W) does not always indicate good energy efficiency.
Power is the rate at which a source generates energy, measured in ergs per second. Obviously, then, because energy is the product of power and time, energy conservation techniques can either reduce the power required to generate light or the total time that the power is being supplied to the light source. Many electric light sources can be used with associated electrical dimming circuits to reduce light output by reducing the power supplied to that source. Photosensors, for example, can be used to dim electric lighting levels when daylight enters a room through a window or a skylight. Time clocks, occupant sensors, and even manually operated switches are effective techniques for turning lights off when a room or a building is unoccupied. Both strategies reduce the energy used for lighting; dimming matches the light source intensity with the needs of the people, and switching extinguishes light when no one needs it. Dimming and switching should be used to reduce only wasted lighting energy. It should be reemphasized that light is necessary for human activity. Our societal goal should not be simply to reduce energy consumption but rather to reduce energy wasted by too much light and by lighting that meets no human need.
Light sources are only rarely used without a fixture to house the light source. A fixture makes handling and operating the light source safer and helps provide
|Common Lamp Types||Typical CCT||Typical CRI|
|RE70 (rare earth phosphor, 70+ CRI)||2700, 3500, 4100, or 5000||70+|
|RE80 (rare earth phosphor, 80+ CRI)||2700, 3500, 4100, or 5000||80+|
|high pressure sodium||2100||24|
light where it is needed by controlling the direction of light emitted by the source. As already noted, electric lamp efficacy is measured in lumens per watt. However, the total flux generated by a source is measured without regard to direction. Because light should be directed toward an object or an area to achieve a purpose, flux emitted from a fixture is not necessarily the most useful photometric quantity to assess efficacy in a given application. An automobile headlamp, for example, should direct as much of the light generated by the lamp as possible onto the road in front of the automobile. The light directed into the night sky cannot be used, and thereby this lost light reduces the fixture (headlamp) efficacy. Therefore, efficacy measured in terms of lumens per watt does not provide a true measure of fixture efficacy because all the flux from the fixture are not always useful for a given application. The photometric quantity, intensity, is the amount of light flowing within an imaginary cone connecting the illuminated object and the light source. Intensity, measured in candelas, is a measure of how much light generated by the light source actually arrives where it is needed. The amount of light arriving at a specific location is critical for headlamp design, for example. In general, intensity per watt is a valuable measure of efficacy for any lighting system because, ultimately, light must arrive at a specified location to be useful. Other light is wasted, and this wasted light should be reflected in a measure of low fixture efficacy. Different fixtures are produced by manufacturers for different applications using a variety of light sources. The most efficacious light fixture for a given application should be used, but the most efficacious light fixture (cdmax /W) does not always employ the most efficacious light source (lm/W).
The term "color" can be used in two ways to describe the light generated by a source or reflected from an object. As already noted, color appearance is a perceptual phenomenon that, despite much scientific investigation, defies precise quantification. For example, the same physical light may look brown or orange depending on its brightness. Further, this same light may look more or less red, yellow, or brown depending on the apparent color adjacent to it. At present we have only a qualitative understanding of these color appearance phenomena. Color can, however, be quantified very precisely in terms of color matching. This system of quantifying color is known as colorimetry. Any light can be matched in appearance with the right combination of idealized, but quantifiable, red, green, and blue lights. These three lights are known as primary colors or, simply, primaries. Color televisions are practical examples of color matching. They can produce a wide gamut of colors through adjustments of three color pixels: red, green, and blue. Thus, although we can predict precisely what colors will match in terms of these three primaries, we have no precise way to predict whether the pixels will be seen as, for example, brown or orange. Through manual adjustments of the color television pixels, however, each person can reach an acceptable appearance of a televised image.
The color of light generated by a source can be precisely described by colorimetry. From a colorimetric description of the light, other color measures can be derived. Two derived measures—correlated color temperature (CCT) and color rendering index (CRI)—are commonly used to characterize light generated by manufactured sources. It is very important to emphasize that both CCT and CRI are derived from the science of color matching but are used, incorrectly, to describe different aspects of color appearance. Despite the technical error, both CCT and CRI have been found to be practically useful by the lighting industry for color appearance.
CCT refers to the appearance of the light generated by a very hot (i.e., incandescent) object, the temperature of which is measured in kelvins (K). As a body is heated, it begins to produce a reddish-yellow, and then a yellow-white light. As temperature increases, the apparent color of the light changes to blue-white. In astronomy, for example, older, cooler stars appear yellow or red, whereas younger, hotter stars look blue. Paradoxically, electric light sources with CCTs between 2,700 K and 3,200 K generate a yellowish-white light and are termed "warm"; those with CCTs between 4,000 K and 7,500 K produce a bluish-white light and are termed "cool." This paradox seems to have originated from the association between yellow light and a hot fire. The association between apparent color and tactile temperature seems to have been reinforced by the cold feel of glass admitting blue light from the sky on a clear day.
CRI is a measure of how "true" or "natural" colors will appear when illuminated by a light source. Light sources that generate light evenly throughout the visible spectrum, such as daylight, have high values of CRI (maximum CRI = 100); those that have gaps in the visible spectrum (e.g., clear mercury) have low CRI. Electric light sources, particularly fluorescent lamps, have undergone a great deal of development in recent years and now have much higher CRI values than were available in 1970. Although real improvements have been made to the color-rendering properties of these lamps, to some extent these lamp developments are only a game of numbers. Given the technical flaws inherent in CRI for describing color appearance, this measure should not be expected to precisely characterize the color-rendering properties of these lamps. For example, a ten-point difference in CRI values is probably unimportant.
TYPES OF LIGHTING
Much of the history of electric light sources (see Figure 3), fixtures (see Figure 4), and control technologies (dimming and switching) centers around improving energy efficiency. It is often assumed that incandescent lamps were the first electric light source. Actually, carbon arc lamps were the first practical electric light source, preceding the incandescent lamp by almost half a century. Carbon arc lamps employ two carbon electrodes separated by a gap. When current is supplied to the electrodes, the lamp produces a very bright, blue-white arc. These lamps literally burn the electrodes while the lamp is operating, so a clock device is required to continuously feed carbon into the arc to keep the gap width constant.
Carbon arc lamps were first developed in the 1840s, and sometimes elaborate towers were created to provide illumination to streets in a few European cities. Carbon arc lamps are still used today for searchlights because they produce the very bright, concentrated point of light needed for a high-intensity beam. These lamps are impractical for other purposes, however, because it is difficult to segregate and distribute this concentrated light into many small packages useful for human activities indoors. Also, cost and the pollution generated by these lamps make them unacceptable by modern standards.
Incandescence means to heat an object to the point of producing light. The incandescent lamp, then, is a lamp with a filament heated to the point of glowing. The trick accomplished by Thomas Edison and his team at Menlo Park, New Jersey, in 1879 was to produce an inexpensive lamp with a carbon filament that would glow for several hundred hours. After more than a year of experimenting, Edison was able to demonstrate an incandescent lamp producing approximately 2 lumens per watt and lasting several hundred hours. Incremental improvements in that basic design, especially the use of the metal tungsten in filaments, have increased the efficacy of commercially available incandescent lamps to between 10 and 15 lumens per watt. More significantly, perhaps, these lamps are easy to install and cost as little as fifty cents each.
It has been argued that Edison's greatest vision was not the invention of the incandescent lamp but rather his insight two years earlier into the possibilities of providing small "packages" of light where people needed them. A high-voltage power supply with a high resistance light source was required to meet his vision; the incandescent lamp was, therefore, a logical outcome of that insight. The incandescent lamp and the associated electrical distribution system changed human history forever. An inexpensive, manageable light source not only illuminated the night but also made it possible to build the large windowless buildings so prevalent today.
One of the major innovations in incandescent lamps has been the tungsten-halogen lamp, developed in 1959. As the tungsten filament of an incandescent lamp glows, some of it evaporates and is deposited on the inside surface of the bulb. This evaporation not only shortens lamp life, but also the deposited tungsten reduces the light output from the lamp. Iodine, bromine, and chlorine are within the family of elements called halogens. These molecules will combine with the evaporating tungsten and, rather than be deposited on the bulb wall, will deposit the combined molecules back onto the filament. At this point the halogen molecule disassociates from the tungsten molecule, and the cycle begins again. The halogen cycle prolongs incandescent lamp life and keeps the lamp burning brightly. Special bulb shapes and materials are needed for tungsten-halogen lamps because very high temperatures are required for their operation. The high temperatures increase efficacy so that most tungsten-halogen lamps available to the market produce approximately 15 to 30 lumens per watt.
Probably every reader has heard of the mythical incandescent lightbulb that has burned for more than fifty years. Because we are all susceptible to believing conspiracy theories, we are suspicious that manufacturers could make all lightbulbs last that long, if only they would. Most inexpensive incandescent lamps available in stores are rated for 750 hours of operation. In reality, an incandescent lamp can be made to last a very long time, certainly longer than 750 hours, but there is no "free lunch." Incandescent lamp life can be prolonged considerably if the lamp is operated at low temperatures. Lamps operated at low temperatures, however, produce relatively more heat than light, so the efficacy drops below the rated 10 to 12 lumens per watt. Lamp life could also be improved if the lamp were more expensive. Incandescent lamps used in traffic signals are rated at about 8,000 hours of operation but are approximately five to ten times as expensive as the conventional household incandescent lamp, because of their more durable filament construction. An incandescent lamp can have long life, high efficacy, or low cost, but not all three at the same time. So although the mythical lamp may exist, and indeed it can be made, physics demands that it must either produce light expensively or inefficiently, and probably both.
Fluorescent lamps were the next major innovation in lamp technology. Introduced commercially in 1938, they were a radical improvement in lighting energy efficiency. At nearly 50 lumens per watt, the first fluorescent lighting systems immediately replaced those using incandescent lamps in large industrial and commercial applications. Even today, fluorescent lamp technologies are arguably the most cost-effective, energy-efficient, and reliable source of illumination for interior applications.
Fluorescent lamps are termed a low-pressure discharge lamp. An electric current passes through mercury contained at normal vapor pressure within the bulb. The current vaporizes the mercury and liberates electrons from the molecules. The liberation of electrons from mercury molecules produces radiation, much of which cannot be seen by humans. Phosphors that coat the inside of the bulb absorb the nonvisible radiation. The irradiated phosphor molecules are themselves excited to liberate electrons that do emit radiation within the visible band of the electromagnetic spectrum. This multistage process sounds inefficient, but fluorescent lamps can be made to operate at nearly 100 lumens per watt, with lamp life greater than 20,000 hours. New lamp designs as well as improvements to the electrical device needed to start and operate the fluorescent lamp, known as a ballast, have improved system efficacy by more than 40 percent since 1980. Not only has efficacy been improved, but also the color characteristics are better, and the audible noise generated by the ballast has been reduced. Moreover, smaller, compact fluorescent lamps have been introduced and are beginning to replace some of the less efficacious incandescent lamps used most commonly in homes.
Many consumers continue to complain about fluorescent lamps, however, arguing that they "buzz," distort the color of natural objects, and cause headaches. These attitudes are barriers to societal goals for energy efficiency, particularly in the home. As stated above, however, most of the technical issues leading to these complaints have been resolved. Nevertheless, these negative attitudes toward fluorescent lamps persist and are, in fact, reinforced by exposure to the older technologies still in operation and by low-cost, inefficient products being introduced by manufacturers from developing countries. A major barrier to widespread introduction of fluorescent lamps is initial price. Fluorescent lighting systems are much more expensive to purchase than incandescent systems. In the long run, however, the energy savings associated with the fluorescent lighting system would more than pay for its higher initial cost.
The flip side of consumer bias is that some people argue that only fluorescent lamps should be used in buildings. This attitude, while well intentioned, is based on an unsophisticated knowledge of the performance of lighting systems. As previously discussed, the efficacy of a lighting system cannot be characterized by lamp efficacy alone. For example, although a fluorescent lamp and ballast may produce 80 lumens per watt compared to a tungsten-halogen lamp at 20 lumens per watt, the system efficacy of a recessed open downlight ceiling fixture may, in fact, be better with a tungsten-halogen source than with a fluorescent source. This perhaps surprising result is due to the fact that the tungsten-halogen filament is very compact. The light from the small tungsten-halogen filament can be optically controlled much easier than it can from the relatively large fluorescent lamp. Where little or no optical control is necessary, as with general illumination from a standing floor-lamp fixture, fluorescent lighting systems are much more efficacious than tungsten-halogen lighting systems in producing the same visual effect. Again, the application is important for selecting the most efficacious lighting system.
Low-pressure sodium lamps, another low-pressure discharge lamp, produce very bright, monochromatic light at relatively high wattage. These lamps are used exclusively for outdoor applications where a high-light-output lamp can distribute light over a relatively large area. Low pressure sodium lamps have the highest efficacy (180 lumens per watt), but as discussed above, provide people with no color perception. Despite its high efficacy, this monochromatic source has made little inroads into the outdoor lighting market, except in the United Kingdom, which consumes approximately half of all low-pressure sodium lamps manufactured.
High pressure can be used to expand the spectral emission of the sodium gas. Although expanding the sodium spectrum reduces the lamp efficacy to between 60 and 120 lumens per watt, it significantly improves the color characteristics of the lamp. High-pressure sodium lamps were introduced in 1965, and the yellow-orange light produced by these lamps is now found throughout modern societies in roadway, security, and parking lot applications. Newer, color-corrected high-pressure sodium lamps can be found in some indoor applications but have still lower efficacies.
High pressure can also be used to expand the spectral emission of mercury gas. High-pressure, clear mercury lamps are no longer widely used because, even under high pressure, they are relatively inefficient and do not provide good color perception. By mixing halides with the mercury under high pressure, however, good color can be produced at relatively high efficacies ranging from 60 to 110 lumens per watt. These metal halide lamps have been gaining steadily in popularity since they were introduced in 1964, particularly as an outdoor light source associated with retail spaces (e.g., shopping centers, gas stations, and facade lighting). These lamps also are being used in many indoor applications, such as warehouses and shopping malls. They are even being used in modern automobile headlamps as a replacement for tungsten-halogen headlamps.
Perhaps the most radical new development in light sources has come from the electronics industry rather than the traditional lighting industry, established in the nineteenth century. Light-emitting diodes (LEDs) were invented in the 1960s, but only since 1997 have these sources become an important light source for widespread applications. Before then, LEDs were used as indicator lights on electronic equipment and were largely restricted to a few colors, the first being the red LED. Today many colors, including white, can be produced economically with efficacies ranging from 5 to 25 lumens per watt. It has been projected that efficacies of some colored LEDs may approach 100 lumens per watt in the near future.
LEDs are a highly directional light source, ideally suited to applications such as automobile taillights and traffic signals. In architectural applications, LEDs have already proven successful in exit sign applications. The high visibility necessary for transportation applications is also a positive attribute in emergency egress fixtures. In addition, the low power requirements of LEDs in exit signs (fewer than 5 or 6 watts per face) compared to other technologies provide substantial energy savings when multiplied by hours of operation typical of exit signs (usually twenty-four hours per day every day). The long life of LEDs also provides the reliability needed for transportation and egress applications.
In the future, LED fixtures will be produced for architectural applications by clustering the individual LEDs. Coupled with electronic controls, the LED fixtures will enable the color and intensity distribution of light to be customized and easily changed. These systems will provide cost-effective and energy-efficient lighting solutions to future lighting artists, designers, and engineers. Indeed, this technology may change architecture in ways not seen since the time of Edison.
The efficient application of lighting technologies to a residential, commercial, or industrial space is much more than simply picking the lamp with the highest lumens per watt. As described above, it is important to have light where you need it and when you need it. Color, cost, ease of maintenance, heat, and durability—as well as how people will use, operate, and maintain the space—are among the other factors to consider in selecting the right lighting equipment for an application.
The world population continues to expand. Fuel reserves continue to be depleted. Pollution associated with power generation continues to increase. Technical advances in light sources, fixtures, and controls as well as those in power generation provide a modestly optimistic picture of the future. In 1850 the extraction efficiency of light from carbon-based fuels such as open gas flames was about 0.04 percent. Today we have increased that efficiency more than a hundredfold. Estimates from the U.S. Department of Energy in 1999 suggest that efficiency improvements in lighting technologies will reduce the required energy for lighting in commercial buildings, although the amount of commercial floor space will continue to grow in the United States. Even if this projection is correct for the United States, the need for light by people around the world will outpace the increased extraction efficiency offered by new lighting technologies in the decade 2000 to 2010.
Our societal ambition to reduce energy consumption is, without any doubt, both correct and urgent. It must always be remembered, however, that humans always will need light. Our goal, then, should be to reduce wasted lighting energy, energy expended on lighting that meets no real purpose. The technological advances in light source efficacy must also be coupled with technological advances in controls—both optical control to deliver light where it is needed, and power control to deliver the right amount of light when it is needed. Lighting control systems are slowly becoming more sophisticated, utilizing both automatic and manual controls, to tune lights to occupant needs. Estimates made in the late 1990s suggest that lighting energy used in offices can be reduced by as much as 80 percent using controls relative to static lighting systems (Maniccia 1999). We must also strive to better understand exactly what humans need. Recommended illumination levels in North America, for example, have been reduced by roughly two-thirds since the oil embargo of 1972, with no noticeable loss in human productivity or satisfaction.
Arguably, a reason why lighting energy is still being wasted is ignorance of policymakers, building owners, and developers. Well-intentioned policymakers legislate power but not energy, failing to consider the importance of lighting controls in meeting our societal goals. They also regulate lamp efficacy rather than lighting system efficacy, implicitly failing to recognize that light should be directed to a location where it can be used. Another reason lighting energy is being wasted is the emphasis on the purchase price of lighting equipment. Often the cheapest lighting products are the most energy-wasteful. A lighting system will be operated for many years, and the cost of energy, even at current low prices, far exceeds the initial cost of even the most expensive lighting equipment.
Mark S. Rea
Bierman, A. (1999). "LEDs: From Indicators to Illumination." Lighting Futures 3(4):1–5.
Bright, A. A. (1949). The Electric-Lamp Industry. New York: Macmillan.
Cox, J. A. (1979). A Century of Light. New York: Benjamin.
Drucker, H. (1997). "1972–1997: Twenty-five Years of Energy and Environmental History: Lessons Learned." In Twenty-Five Years of Energy and Environmental Policy: Proceedings of the 25th Annual Illinois Energy Conference. Chicago: University of Illinois at Chicago, Energy Resources Center.
Howell, J. W., and Schroeder, H. (1927). History of the Incandescent Lamp. Schenectady, NY: Maqua.
Illuminating Engineering Society. (1947). IES Lighting Handbook, 1st ed. New York: Author.
Illuminating Engineering Society. (1952). IES Lighting Handbook, 2nd ed. New York: Author.
Illuminating Engineering Society. (1993). IES Lighting Handbook, 8th ed. New York: Author.
International Lighting Review. (1979). "1879–1979 [Edison Lamp Centenary Issue]" 30(1):1–13.
Leslie, R. P., and Conway, K. M. (1996). The Lighting Pattern Book for Homes, 2nd ed. New York: McGraw-Hill.
Leslie, R. P., and Rogers, P. (1996). Outdoor Lighting Pattern Book. New York: McGraw-Hill.
Lighting Research Center. (1994). A&P Food Market, Old Lyme, Connecticut, DELTA Portfolio 1(1). Troy, NY: Rensselaer Polytechnic Institute.
Lighting Research Center. (1994). Linens 'n Things, Patchogue, New York, DELTA Portfolio 1(2). Troy, NY: Rensselaer Polytechnic Institute.
Lighting Research Center. (1995). 450 South Salina Street, Syracuse, New York, DELTA Portfolio. 1(3). Troy, NY: Rensselaer Polytechnic Institute.
Lighting Research Center. (1996). DeGraff Street Industrial Center, Amsterdam, New York, DELTA Portfolio 1(4). Troy, NY: Rensselaer Polytechnic Institute.
Lighting Research Center. (1996). Prudential HealthCare, Albany, New York, DELTA Portfolio 1(5). Troy, NY: Rensselaer Polytechnic Institute.
Lighting Research Center. (1997). Sacramento Municipal Utility District Customer Service Center, Sacramento, California. DELTA Portfolio, 2(2). Troy, NY: Rensselaer Polytechnic Institute.
Lighting Research Center. (1997). Sony Disc Manufacturing, Springfield, Oregon. DELTA Portfolio 1(6), 2(1). Troy, NY: Rensselaer Polytechnic Institute.
Lighting Research Center. (1998). Mary McLeod Bethune Elementary School, Rochester City School District, Rochester, New York. DELTA Portfolio, 2(3). Troy, NY: Rensselaer Polytechnic Institute.
Lighting Research Center. (1999). South Mall Towers Apartments, Albany, New York. DELTA Portfolio, 2(4). Troy, NY: Rensselaer Polytechnic Institute.
Lighting Research Center. (1999). Staples Distribution Center, Killingly, CT, DELTA Portfolio 2(5). Troy, NY: Rensselaer Polytechnic Institute.
Lighting Research Center. <www.lrc.rpi.edu>.
Lightolier. (1994). Journey: Lightolier and Lighting in the Twentieth Century. New York: Lightolier.
Luckiesh, M. (1920). Artificial Light. New York: Century.
Maniccia, D.; Ratledge, B.; Rea, M.; and Morrow, W. (1999). "Occupant Use of Manual Lighting Controls in Private Offices." Journal of the Illuminating Engineering Society 28(2):42–56.
O'Dea, W. T. (1958). A Short History of Lighting. London: HMSO, Ministry of Education, Science Museum.
Rea, M. S., ed. (1991). Selected Papers on Architectural Lighting. Bellingham, WA: SPIE—The International Society for Optical Engineering.
"Lighting." Macmillan Encyclopedia of Energy. . Encyclopedia.com. (September 11, 2018). http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/lighting
"Lighting." Macmillan Encyclopedia of Energy. . Retrieved September 11, 2018 from Encyclopedia.com: http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/lighting