Online Encyclopedia Search Tool

Your Online Encyclopedia


Online Encylopedia and Dictionary Research Site

Online Encyclopedia Free Search Online Encyclopedia Search    Online Encyclopedia Browse    welcome to our free dictionary for your research of every kind

Online Encyclopedia


IMAX (for Image Maximum) is a film projection system which has the capacity to display images of far greater size and resolution than conventional film display systems. A standard IMAX screen is 22 m wide and 16 m high, but can be larger. IMAX is the most successful large-format special-venue film presentation system.



The desire to increase the visual impact of film has a long history. Cinemascope and Vistavision widened the projected image from 35 mm film, and there were multi-projector systems such as Cinerama for even wider presentations. While impressive, Cinerama was cumbersome, difficult to set up and the joins between the screens were difficult to hide.

Technical Aspects

The intent of IMAX is to dramatically increase the resolution of the image by using much larger film stock. To do this, 70 mm film stock is run "sideways" through the cameras. While traditional 70 mm film has an image area that is 48.5 mm wide and 22.1 mm tall (for Todd-AO), in IMAX the image is 69.6 mm wide and 48.5 mm tall. In order to expose at standard film speed of 24 frames per second, three times as much film needs to move through the camera each second.

Drawing the large-format film through the projector was a difficult technical problem to solve; conventional 70 mm systems were neither steady enough for the 586x magnification. IMAX projection involved a number of innovations. William Shaw of IMAX adapted an Australian patent for film transport called the "rolling loop" by adding a compressed-air "puffer" to accelerate the film, and put a cylindrical lens in the projector's "gate" for the film to be vacuumed up against during projection. (The "field flattener" because it served to flatten the image field) IMAX projectors are pin-stabilized, meaning 4 registration pins engage the sprockets at the corners of the projected frame to insure perfect alignment. Mr. Shaw added cam-controlled arms to decelerate each frame to eliminate the microscopic shaking as the frame "settled" onto the registration pins. The projector's shutter is also open for around 20% longer than in conventional equipment and the light source is brighter, the largest 12-18 kW lamps have hollow, water-cooled electrodes. An IMAX projector is therefore a substantial piece of equipment, weighing up to 1.8 tonnes.

IMAX uses a stronger "ESTAR" (Kodak's tradename for DuPont's MylarŪ) base. The reason is not for strength, but precision. Estar does not change size due to the chemicals used to develop the image, and IMAX's pin-registration (esp. the cam mechanism) is intolerant of either sprocket-hole or film-thickness variations. The IMAX format is generically called "15/70" film, the name referring to the 15 sprockets per frame of 70 mm stock. The bulk of the film requires large platters rather than conventional film reels.

IMAX film does not include an embedded soundtrack in order to use more of the image area. Instead the IMAX system specifies a separate six-channel 35mm magnetic tape synchronized to the film. (This original system--35mm mag tape locked to a projector--was commonly used to "dub" or insert studio sound into the mixed soundtrack of conventional films.) By the early 90's, a separate digital 6-track source was synchronized using a more precise pulse-generator as a source for a conventional SMPTE timecode synchronization system. This development presaged conventional theatrical multichannel sound systems such as Dolby Digital and DTS.

Further improvements and variations on IMAX include a dome projection option (OMNIMAX), several 3-D presentation methods, and the possibility of a faster 48 frames per second rate. Improvements in the sound systems have included sample-synchronized CD sound, a 3D sound system, and the elliptical-pattern speaker-clusters.

IMAX theater construction also differs significantly from conventional theaters. The increased resolution allows the audience to be much closer to the screen, typically all rows are within one screen-height. (Conventional theaters seating runs 8 to 12 screen-heights) Also, the rows of seats are set at a steep angle (Up to 23 degrees in some domed theaters) so that the audience is facing the screen directly.

Viewer experience

For the viewer, these technical differences result in a much more immersive, engaging experience than conventional film projection. The large screen and close seating mean that much of the viewer's field of vision is filled with the image, and the high resolution and positional stability of the film format imparts a sense of reality and detail. IMAX film can be overwhelming at times, with some viewers experiencing motion sickness during scenes with significant motion.


The IMAX system was developed by three Canadians: Graeme Ferguson, Roman Kroitor and Robert Kerr. During Expo 67 in Montreal, their multi-projector giant-screen system had a number of technical difficulties that lead them to design a single-projector/single-camera system. The first IMAX film was demonstrated at Expo '70 in Osaka, Japan. The first permanent IMAX system was set up in Toronto in 1971. As of May 2003, there were 230 IMAX theatres in 34 countries around the world. Half of these are commercial theaters and half are in educational venues.


Although IMAX is an impressive format from a technical perspective, its popularity as a motion picture format has traditionally been limited. The expense and logistics of producing and presenting IMAX films has dictated a shorter running time compared to conventional movies for most presentations (typically around 40 minutes). The majority of films in this format tend to be documentaries ideally suited for institutional venues such as museums and science centers. IMAX cameras have been taken into space aboard the Space Shuttle, to Mount Everest, to the bottom of the Atlantic ocean, and to the Antarctic to film such documentaries.

Some IMAX theaters had shown conventional films (using conventional projection equipment) as a sideline to the native-IMAX presentations. In the late 1990s there was a wave of interest in broadening the use of IMAX as an entertainment format. A few pure-entertainment IMAX short films have been created, notably which had a successful run in 1998 and Haunted Castle, released in 2001 (both of these were IMAX 3-D films). In 1999, Disney produced Fantasia 2000, the first full-length animated feature released exclusively in the IMAX format (the film would later have a conventional-theatrical release). Disney would also release the first 2-D live-action native IMAX entertainment film, The Young Black Stallion , in late 2003.

In the fall of 2002, IMAX and Universal Studios released a new IMAX-format of the 1995 theatrical film Apollo 13. This release marked the first use of the IMAX-proprietary "DMR" re-mastering process that allowed conventional films to be converted into IMAX format. Other theatrically-released films, including a Star Wars installment, would subsequently be re-released at IMAX venues using the DMR process. Because of a technical limitation on the size of the film reel, these early DMR releases were edited to conform to a two-hour length limitation. In 2003 a notable IMAX re-release, again using the DMR process, was The Matrix Reloaded. Later in 2003, the sequel Matrix Revolutions was the first feature film to be released simultaneously in IMAX and conventional theaters.

Reviewers have generally praised the results of the DMR blowup process, which have superior visual and auditory impact to the same films projected in 35 mm. A typical comment on "Apollo 13" notes "The big effects moments, explosive sound mix, and James Horner's soaring score are all amazing in IMAX." DMR blowups are not, however, comparable to films created directly in the 70mm 15-perf IMAX format. Big-screen aficionados note that the decline of Cinerama coincided roughly with the supercession of the original process with a simplified, reduced-cost, technically inferior version, and view DMR with alarm. IMAX originally reserved the phrase "the IMAX experience" for true 70 mm productions, but now allows its use on DMR blowups as well.

Noted feature film director James Cameron filmed a movie about the Titanic in 3D IMAX format, Ghosts of the Abyss .

Up to 2002, eight IMAX format films have received Academy Awards nomination with one win, the animated short, The Old Man and The Sea in 2000.

Many IMAX films have been remastered into HDTV format for the INHD channels.

List of Notable IMAX Films

List of Feature Films Released on IMAX Screens

Technical Specs

IMAX (15/70)

  • spherical lenses
  • 15 perforations per frame
  • horizontal pulldown, from right to left (viewed from base side)
  • 24 frames per second
  • camera aperture: 2.772" (70.41 mm) by 2.072" (52.63 mm)
  • projection aperture: at least 0.80" less than camera aperture on the vertical axis and at least 0.016" less on the horizontal axis

Omnimax Same as IMAX except

  • special fisheye lenses
  • lens optically centered 0.37" above film horizontal center line
  • projected elliptically on a dome screen, 20 degrees below and 110 degrees above perfectly centered viewers

Notable IMAX venues

External links

Last updated: 10-26-2004 16:51:05