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A variation of IMax, IMax Dome (originally called OmniMax), is designed for projection on tilted planetarium domes.
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.
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 xenon-arc 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 MylarŪMylar is a trade name of DuPont Teijin Films of Hopewell, VA for biaxially-oriented polyethylene terephthalate (BOPET) polyester film used for its high tensile strength, chemical and dimensional stability, transparency, and electrical insulation. A variet) 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 soundtrackGenerally speaking, the term soundtrack refers to the recorded sound in a motion picture. In terms of film formats, the soundtrack is the physical area of the film which records the synchronized sound. The term soundtrack is also commonly used to refer to 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 DigitalDescription Dolby Digital is the trademark for Dolby Laboratories' AC-3 lossy audio compression (or data reduction) system. It is a system for coding and decoding ( codec) digital audio sound so that it occupies less space on the recording medium. It is t and DTSIn cinemas, DTS Digital Theater Systems is a multichannel audio source for synchronized film sound. A modified time code is optically imaged on the film itself, and the DTS processor uses this to synchronize the soundtrack audio which is recorded in a com.
Further improvements and variations on IMAX include several 3-D3-D or 3D abbreviates "three dimensional" and is often related to a stereoscopic display that exploits binocular vision. Three dimensional objects have volume and may be measured and described using three orthogonal directions. In animation, 3-D sometimes presentation methods and the possibility of a faster 48 frames per secondFrame rate or frame frequency, is the measurement of how quickly an imaging device can produce several consecutive images, called frames. It applies to computer graphics, to video cameras, to film cameras, and to input devices such as motion picture film 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.