IMAX

Film stock and cameras

IMAX was originally defined by the use of its proprietary 15/70 IMAX film, which runs through the projector horizontally—unlike most other film stock. The numbers indicate the dimensions of the film frame: The width of the film strip—which dictates the height of the frame—is 70 millimeters (mm), and each frame spans 15 equidistant perforations (perfs) or sprocket holes, which run along the sides of the film across its length. The usable image area of each frame is 69.6 mm × 48.5 mm—about 10 times that of a standard 35-mm frame and thrice as large as that of a 5-perf 70-mm frame. This larger image area allows for much more photographic information to be captured, which translates to a larger, sharper image with greater detail and low film grain (sandlike texture caused by light-sensitive particles in the film). Because of their massive size, film reels including IMAX shots can be unusually long and heavy. For instance, the IMAX print of Oppenheimer (2023) was 11 miles (about 18 kilometers) in length and weighed 600 pounds (about 270 kilograms).

Discover how ordinary objects work, and expand your understanding of the familiar.

SIGN UP

" height="20" alt="HEW Logo">

Thank you for signing up!"

Back to homepage

By clicking "Sign Up", you consent to the Britannica Privacy Policy and Terms of Use.

IMAX cameras shoot on 65-mm film negatives, which also roll through the camera horizontally. The horizontal orientation of the film strip is the key to IMAX’s impressive detail, allowing the camera to capture images on a much larger surface area than that on vertically oriented 65-mm film, whose frame height generally spans 5 or 8 perfs. The negatives are then printed as positives on the 70-mm prints for projection. The additional 5-mm is used to print frame information. The final print does not contain a soundtrack; the audio is generally synced and played digitally during projection. When composing shots for IMAX, filmmakers often choose to frame the main subject or action in the center of the image for two reasons: First, the taller IMAX image will likely be cropped at the top and bottom later for wider non-IMAX screens, so keeping things centered helps ensure important visual information is not cropped out. Second, it avoids forcing audiences to keep track of action across the extreme edges of large IMAX screens, which may cause physical discomfort.

As of the mid-2020s there were probably fewer than 10 operational IMAX film cameras, though the company does design new bodies from time to time—often with input from notable directors and cinematographers. These cameras require specially made lenses. Because of the mechanical complexity required to pull the large film stock through these cameras, the cameras are known to be notoriously expensive, heavy, and loud. Because of the noise these cameras create, filmmakers have long found it difficult to film dialogue scenes with them, and the format is often reserved for only a few key scenes, which are stitched between longer segments filmed on smaller formats. However, the Keighley, a new camera system quieter than earlier versions, was developed to film Nolan’s 2026 action adventure The Odyssey—the first feature to be shot entirely on IMAX film.

IMAX has also developed digital 2D and 3D cameras in partnership with other companies.

Filmed for IMAX vs. shot with IMAX cameras

The labels “filmed for IMAX” and “shot with IMAX cameras” refer to the kind of cameras a movie used and the associated production processes. In 2020 the company launched the “filmed in IMAX” (later renamed “filmed for IMAX”) program, under which it authorizes specific digital camera models to shoot movies certified for screening in its theaters by following specific guidelines. Only a handful of top-tier, large-sensor digital camera models have been approved under the program, including those made by ARRI, RED, Sony, and Panavision. For films shot under the program, IMAX offers its expertise throughout the production and ensures that they are shot with an aspect ratio of 1.90:1 or 1.43:1 to fit its theater screens. The program has allowed for more IMAX productions to be released every year. By contrast, movies shot on 15/70 IMAX film stock using specialized IMAX cameras have subsequently been branded as “shot with IMAX film cameras,” which indicates much higher-quality images, especially when paired with analog projection.

Explore Britannica Premium!

The trusted destination for professionals, college students, and lifelong learners.

SUBSCRIBE

IMAX theaters and projection

IMAX theaters are typically characterized by larger, taller screens than those of standard cinemas, because they are optimized to fit the aspect ratios of IMAX cameras. Many IMAX auditoriums also have steeply tiered seating and are designed to produce high-quality audio with clearer bass and treble and with very little distortion. The biggest IMAX screens can be about 100 feet (30 meters) wide and more than 70 feet (21 meters) high. Only a small number of these IMAX theaters have a 1.43:1 aspect ratio, as most new digital theaters after 2008 have adopted the slightly wider 1.90:1 aspect ratio. However, some IMAX-branded theaters have retrofitted screens that are much smaller than those of its purpose-built cinemas and feature lower-resolution digital projectors, leading them to be pejoratively termed “LieMAX” by critics.

Analog 15/70 IMAX film projection—called IMAX Grand Theater (GT)—yields exceptionally sharp and detailed images. There are only about 30–45 screens equipped with the highest-quality mechanical IMAX projection in the world—most of them in the United States. To accommodate the massive film reels and prints, the projection system is also sizable. It uses a vacuum to pull and orient the film, which moves much faster through the projector than ordinary 35-mm film. Compared to 35-mm projection, the shutter of the GT projector stays open for a slightly greater duration, allowing the light from a powerful xenon short-arc lamp to shine through the film for longer to produce brighter images. IMAX also has a projector system for 3D films and one called a “small rotor” projector for slightly smaller screens.

The vast majority of IMAX screens worldwide are fitted with digital projectors. IMAX’s highest-end digital system, IMAX GT Laser, uses two laser projectors with 4K resolution (4,000 horizontal pixels) in combination to display large images at a 1.43:1 or 1.90:1 ratio. The resolution of the image and picture quality, however, are inferior to those of the GT film projector. Laser projectors still beat out the older IMAX digital xenon 2K resolution projectors, which were retrofitted into existing theaters. IMAX also offers lower-resolution systems with only a single projector (Laser XT and Commercial Laser).

IMAX also operates IMAX Dome or Omnimax theaters, which are geared mostly toward educational spaces such as planetariums and museums. Their specialized projection systems can be analog or digital and are modified to fit the size and shape of large, hemispherical screens.