Film Guides / Film formats and cinema tech
IMAX explained
What makes IMAX different from a normal big screen: the giant 15/70 film frame, the taller 1.43:1 image, laser projection and the sound system.
IMAX is the best-known premium cinema format in the world. It began as a Canadian invention for world fairs and science museums and became the most sought-after way to see a blockbuster. The name has come to mean a giant screen, but the details vary a lot between venues.
Where IMAX came from
IMAX was developed in Canada in the late 1960s by a group of filmmakers and engineers including Graeme Ferguson, Roman Kroitor, Robert Kerr and William Shaw, after multi-screen films at Expo 67 in Montreal showed the public's appetite for immersive images. The first IMAX film was shown at Expo 70 in Osaka, Japan. The first permanent IMAX theater, the Cinesphere, opened at Ontario Place in Toronto in 1971.
For decades IMAX meant mostly documentaries about nature, space and science, often 40 minutes long, shown in museums. From the early 2000s, Hollywood features began to be released in IMAX, and some directors started filming sequences with IMAX cameras.
The 15/70 film frame
Classic IMAX film runs 70mm film horizontally through the projector, with each frame 15 perforations wide. That is why the format is called 15/70. The frame is about ten times the area of a standard 35mm frame and roughly three times the area of a standard 70mm frame (see 35mm and 70mm).
Moving such large frames smoothly needs a special projector mechanism. Rather than pulling the film with sprocket teeth alone, the IMAX projector uses a "rolling loop" system and holds each frame flat against the lens with a vacuum.
Aspect ratios in IMAX
| IMAX presentation | Aspect ratio | Where you find it |
|---|---|---|
| IMAX 70mm film | 1.43:1 | A few dozen venues worldwide with film projectors |
| IMAX with Laser (large screens) | Up to 1.43:1 | The largest flagship IMAX screens |
| IMAX digital (most multiplex IMAX) | 1.90:1 | Most IMAX screens in shopping centers and multiplexes |
| Standard scope release | 2.39:1 | Regular cinema, shown letterboxed inside IMAX screens |
Films shot partly with IMAX cameras often switch ratios: the image expands to fill the taller screen for selected sequences, then returns to the wider frame. This is called expanded aspect ratio. More on ratios in aspect ratios.
Digital and laser IMAX
IMAX introduced digital projection in 2008 to bring the format to many more cinemas. Digital IMAX typically uses two projectors overlapping on one screen for brightness and sharpness. IMAX with Laser, introduced in the mid-2010s, uses laser light sources for higher brightness, deeper contrast and a wider color range. Laser systems can project the full 1.43:1 image on suitably shaped screens.
IMAX releases also go through a remastering process called DMR (Digital Media Remastering) that prepares each film for IMAX projection and sound.
IMAX sound
IMAX theaters use their own sound systems with precisely calibrated speakers. Newer IMAX with Laser systems often use a 12-channel layout that adds side and overhead channels. The audio is mixed specifically for the IMAX release.
Is every IMAX the same?
No. Screen sizes range from a little bigger than a normal premium screen to giant screens several stories tall. Before booking, check:
- Screen size and shape: a 1.43:1 screen shows the full expanded image; a 1.90:1 screen crops it.
- Projection type: laser or xenon digital, or 70mm film for special releases.
- Seat position: in tall screens, sit around two-thirds of the way back and near the center. See seats and formats.
If a film was "filmed for IMAX" and you can choose between venues, pick the one with a 1.43:1 screen to see the full picture the director framed.
