IMAX Technology

Ask anyone who has seen an IMAX film in an IMAX theater to describe their experience, and they will probably use words like "huge," "giant," and "awesome." This reaction is exactly what the designers of the IMAX film technology had in mind—a motion picture experience like no other. What exactly is it that makes IMAX films so different?

IMAX's History

In the late 1960s, filmmakers experimented with multiple-screen films. They used up to three cameras to film movies in a very wide format, which could then be played back to an audience using three projectors at three times the normal width. However, these systems had many problems. First, three cameras had to be used simultaneously to film the movie. Then the three projectors that were used to show the film had to be perfectly aligned and synchronized. Another problem was that the edges of each projector's image tended to vary in brightness.

Knowing that multiple-screen films were very popular with audiences, a group of Canadian filmmakers and business people decided to design a system that had the same large-scale effect as a multiple-screen film, but with a single camera and projector. After several years of work, the first IMAX film premiered at the 1970 World Expo in Osaka, Japan. The whole system was a hit, and since that time IMAX theaters have been built and are in use all over the world.

The Characteristics of IMAX

The magic of IMAX motion pictures stems from the combination of specialized equipment that is used to film and project IMAX movies. Every part of the system has been developed especially for IMAX films.

Screen Size. The first thing an IMAX theater patron is likely to notice is the screen size. The typical IMAX screen is about 50 feet tall and 70 feet wide. With this large screen, and the positioning of the seats in the theater, the screen fills even the peripheral vision of the audience. So when the camera moves, the audience experiences the sensation of movement. The sensation of motion can be made more spectacular when the film has been shot at high speeds, like from the cockpit of a jet fighter or from the front car on a roller coaster.

Some IMAX flat screens are as large as 100 feet high. Even more spectacular are IMAX dome screens. IMAX dome screens can be almost 90 feet in diameter. In the dome, the audience sits at a reclined angle so that spectators look up at an angle toward the center of the domed screen. Even in flat-screened IMAX theaters, the audience area is designed so that every seat has a full, unobstructed view of the screen. In an IMAX theater, patrons feel like they are in the movie, rather than just watching it.

Sound System. Nearly everyone has experienced some sort of surround sound system in regular movie theaters, but IMAX theaters have sound systems that are loud enough and spectacular enough to complement their unique visual experience. IMAX theaters have six-channel wrap-around sound systems. That means up to six different audio tracks can be channeled anywhere in the theater to give the audience the perception that not only are the images in motion, but so are the sounds. With up to 13,000 watts of power driving dozens of speakers, the sound systems are loud enough to recreate the concussion that is felt during a space shuttle launch.

Film Size. Motion picture film is divided into frames. In the camera, the film is moved behind the lens and shutter and each frame is exposed for just a moment. When the film is developed and played back in a projector, the moving frames recreate the motion that was captured by the camera.

The size of the film frame affects the quality of the image that is produced. Standard motion picture film is 35 mm (millimeters) wide, and has a height of 4 perforations. The perforations are tiny holes on the edges of the film that the camera and projector use to move the film. High-quality motion picture film is 70 mm wide and has a height of 5 perforations. IMAX film is even larger. It is 70 mm wide and has a height of 15 perforations. Additionally, IMAX film is run through cameras and projectors horizontally, so the perforations are at the top and bottom of the frame. Regular film is run through the cameras and projectors vertically, so the perforations are on the sides of the frame. Because of its size, IMAX film is often referred to as 15/70 film.

Special Cameras. IMAX movies are not just regular movies that have been printed on 15/70 film. The making of an IMAX movie begins with filming, during which special IMAX cameras use 15/70 film. The cameras weigh over 50 pounds apiece, and the film is loaded in cartridges that weigh about 5 pounds. Because of the speed of the IMAX film in the cameras, each film cartridge will provide only 5 to 7 minutes of footage. This makes for quite a bit of film reloading, or the use of multiple cameras.

Mega Projectors. The projectors used to produce the unparalleled IMAX movie experience have been compared in size to a compact car. To begin, the film is loaded into the projector on reels that are the size of truck wheels. The reels are mounted horizontally on either side of the projector because IMAX film moves horizontally instead of vertically. The film itself moves through the projector in a unique way that is called a "rolling loop." Air is used to hold each frame momentarily on the rear of the lens, producing a picture that is far more steady and clear than a normal motion picture projector.

To produce an image bright enough to light up the giant IMAX screens, the projectors use special xenon bulbs that consume up to 15,000 watts of power. This is equivalent to 150 100-watt light bulbs. With a bulb so bright, special measures must be taken to cool the projector. Both air, flowing at 800 cubic feet per minute, and water, flowing at 5 gallons per minute, cool the bulb, which can have a surface temperature of 1,300° F.

IMAX Movies

Because of the expense and technical difficulties of filming IMAX movies, most of the 110 or so films that exist are short films, 40 minutes or less in length. Due to the spectacular visual quality of the IMAX format, many films are documentaries that are intended to show the audience images that are normally inaccessible. Consequently, the impact of the films about space exploration, wildlife, wilderness areas, or extreme environments is unforgettable.

The IMAX film system is a remarkable experience for audiences all over the world. Since everything about the system is like a regular movie multiplied by several factors, perhaps the adage "bigger is better" really applies to the IMAX system.

see also Ratio, Rate, and Proportion.

Max Brandenberger

Internet Resources

IMAX Motion Picture Systems. <http://www.1570films.com/imax.htm>.

IMAX Corporation. <http://www.imax.com>.

"IMAX—Above the World and Below the Sea." The Tech Museum of Innovation. <http://www.thetech.org/ops/imax/imax_overview.html>.

DOES FILM SIZE MATTER?

The area of an IMAX film frame—the area that is exposed—is over ten times larger than 35 mm (millimeter) film, and over three times larger than standard 70 mm film. This extra area makes the images sharper and more vibrant than other film formats.