The evolution of a medium

Few other manufacturers dominate their business the way Imax Corp. dominates large-format production. From the moment a filmmaker loads a camera to the moment a movie patron dons a set of 3D goggles, Imax has its hand in the production process,...

Few other manufacturers dominate their business the way Imax Corp. dominates large-format production. From the moment a filmmaker loads a camera to the moment a movie patron dons a set of 3D goggles, Imax has its hand in the production process, if not entirely, then at least at points along the way.

The first lf projector – developed by Imax in 1968 – still runs at Toronto’s Cinesphere and the technology developed from that point on at the company’s Mississauga, Ont., headquarters acts as ra oadmap to the evolution of the medium.

Here, then, is a list of the innovations that have defined large format:

The camera: Commissioned by Imax in 1968, Norwegian inventor Jan Jacobson built the prototype imax movie camera in two and a half months. The camera uses the world’s largest film stock, a 15-perforation, 70mm frame, that is 10 times the size of a conventional 35mm film frame.

The projector: imax projectors use a ‘rolling loop’ system invented by Australian Ronald Jones that horizontally advances the film in a wave-like motion. Each frame is positioned on fixed registration pins and the film is held firmly against the rear element of the lens by a vacuum. The film runs through at 24 frames per second. The projection lamp is 15,000 watts, bright enough to be seen from outer space.

The screen: The giant screen, which reaches up to eight stories high, is perforated with thousands of tiny holes to allow sound to flow through unimpeded.

The sound: imax uses a six-channel, multi-way digital sound system, manufactured by Sonics Associates, with strategically placed speakers behind the screen – above, below, right, left, plus a sub-bass. Another two speakers reside outside the screen to surround the viewer in sound.

The 3D camera: Two lenses are precisely spaced to match the distance between human eyes. This interocular distance allows each lens to capture a left- and right-eye view of an object. The images register onto two separate rolls of film which run simultaneously through the camera.

The 3D GT Projector: To enable 3D, twin lenses alternately project left- and right-eye images that run on a dual strip of film. The strips run through at 24 fps while the shutters alternate between left- and right-eye images 96 times per second. The gt is water cooled and weighs 2,000 pounds.

The 3D SR Projector: Built for smaller theatres of 270 seats or less, the air-cooled sr is actually two scaled-down imax ‘rolling loop’ projectors which are pushed together to project in 3D or moved apart so that one can project 2D.

The Universal Paint Rig: The Universal Paint Rig is a fully automated paint robot designed by Imax to paint high-gain 3D screens. The rig consists of an x-y plotter with a third z-axis that tracks the curve of the giant screen. The robot sprays a metallic water-based paint evenly onto the giant screen, a requirement to optimize light reflection and enhance the 3D experience.

The 3D electronic glasses: Electronic liquid-crystal shutter glasses sense an infra-red signal from the projection system causing the shutters to alternately open and close 48 times per second, allowing each eye to see the appropriate image.

The 3D polarized glasses: Images are projected through polarized projector lenses and then reflected back through the glasses, which have the same polarized alignment in each lens. The left eye transmits only left-eye images and the right only right-eye images.

The Personal Sound Environment: The imax pse system allows the filmmaker to enhance drama and suspense by placing the sound anywhere in front, behind or above the viewer, thus creating sound which is connected to the 3D images being projected. This essentially adds two channels to the six-channel sound system.