IMAX

IMAX is a film projection system which has the capacity to display images of far greater size than conventional film. A standard IMAX screen in 22m wide and 16m high, but can be larger.

The desire to increase the visual impact of film has a long history. Film formats such as Cinemascope and Vistavision developed the image and in the late 1960s there were attempts at multi-projector[?] systems. While impressive the system was cumbersome, difficult to set up and the joins between the screens were difficult to hide.

The IMAX (IMage MaXimum) was developed by three Canadians - Graeme Ferguson, Roman Kroitor and Robert Kerr. It uses a special 70mm/15 film stock (sometimes called "15/70" film, to distinguish it from conventional films that are also shown at some IMAX theatres), which is three times the size of conventional 70mm stock, has three times as many perforations, is a different ratio, stronger and does not carry a sound track[?].

Drawing the film through the projector was a difficult technical problem to solve, using a conventional system simply tore the film apart and was unable to hold the film flat to the lens. IMAX required a number of innovations - the film runs horizontally with a ripple technique called rolling loop, the film moves in a wave with each frame being held flat onto the projection elements by a field flattener vacuum. The shutter is also open for around 20% longer than in conventional equipment and the light source is brighter and requires water-cooling. An IMAX projector is therefore a substantial lump, weighing up to 1.8 tonnes. Further improvements to the technique include a dome projection option (OMNIMAX) and the possibility of a faster 48 fps rate. While IMAX does not include a sound-track it has specified a separate six-channel sound system.

The first IMAX film was demonstrated at EXPO '70 in Japan. The first permanent IMAX system was set up in Toronto in 1971. Although an impressive format it is not commercially popular, apart from specialist films to demonstrate the format no major release movies have been made in IMAX format and very few of any kind have been made since the initial burst of enthusiasm in the 1970s. There are around 200 IMAX theatres in the world.

External link

• IMAX - official site (http://www.imax.com/)