Click on image to see full size
The Canadian IMAX system of cinematography is considered to be the largest motion picture in the world, and its very name is a synonym of Maximum Image relating to the 48.5mm x 69.5mm frame size when 70mm film is projected horizontally. Screen sizes of 60ft x 80ft or larger are commonplace in IMAX cinemas, and viewing such large screen images accompanied by multi-channel sound is an exciting experience. The basic principle of IMAX projection can be traced not to Canada, America or even Europe, but to a small workshop on the other side of the world in Australia.
For almost 100 years, engineers in the motion picture industry have come up with nothing better than either a simple claw movement or an intermittent sprocket to transport film through a projector. This works well for film sizes up to and including conventional 70mm, but problems occur with acceleration loads on wider films which can cause unsteadiness and a very short print life.
Over in Brisbane, Australia, there was an engineer called Ron Jones who had always been fascinated by cinematograph equipment. He owned a repair workshop and back in the 1960's he had been working on an entirely new film transport system. He found that he could advance film through a projector in gentle caterpillar like waves on to fixed registration pins using compressed air jets to cushion the film movement. Ron called his unique system 'The Rolling Loop' and immediately took out a patent.
At about the same time producer/cameraman Graham Ferguson and his partner Roman Kroiter were making multi-screen films for the Canadian Government, often using several 35mm cameras strapped together. Their dream was to find a large format system which would produce a single image on a giant screen, with audiences sitting relatively close so that the projected image covered the entire field of vision of the viewer. This concept was quite different from normal viewing practice, and meant that the back row of the audience would have to be sitting at a distance closer than the width of the screen. The problem always returned to the system of projection, and both Graham and Roman visited the New York World Fair to see a 70mm film with a 10 perforation pull-down. Even this was not big enough for their purpose, and when they eventually heard about the Rolling Loop patent they realised that this might just be the answer. Graham was on the next plane to Brisbane.
Ron Jones was rather taken aback by the sudden interest in his system, and whilst Graham thought that all Hollywood would be there clamouring for the patent rights, he was in fact the only one. So without any competition he bought the world rights and returned to Canada with the prototype for a revolutionary new film transport system.
The catalyst which hastened the development of IMAX was an invitation from Japan to premiere the new system at Osaka's 1970 Exposition, which was barely two years away. The invitation was accepted and the race began. Graham and Roman decided that they would have to make use of the commercially available 70mm film but run it in a horizontal plane. To provide a suitable image ratio, they agreed to have a 15 perforation pull-down (or pull-across).
The design of the IMAX projector posed many problems if it was not to tear the film to shreds and abort the project. Full marks must go to the development engineer Bill Shaw who appeared to be capable of solving everything even though he had had no previous experience of film technology. In the final design the film is accommodated on a large 'cake stand' platter, and sprocket fed into a large circular rotating gate. Air jets control the rolling loop and ;'float' the film through a fixed channel leading to the projection aperture. The registration pins ensure a rock steady picture, and a vacuum at the aperture holds the film against the rear element of the projection lens to ensure a sharp all over focus.
Because of the extremely large screen and relatively short throw, a wide angle projection lens was required which would cover a picture area at an angle of 70 degrees from corner to corner, and no such lens existed for such a large projector. The problem was given to Ernest Leitz (Canada) Ltd who eventually designed and built a lens in 11 months. The standard IMAX lens has a diameter of 88mm, and is unique in that the two rear elements are in contact with the film and therefore outside the lens barrel.
Normal projector lamp houses were just not sufficient for the large screen sizes envisaged, and the illumination finally selected was a 12kW water cooled Xenon lamp developed by the US military for its searchlights. Although the light output was sufficient for the IMAX projector, the amount of heat generated was enough to cause a 2Õ x 4Õ piece of wood held at or near the film plane to burst into flames! Bill Shaw's solution was a water cooled metal mirror behind the lamp as a heat sink to absorb infrared and a supplementary 'cold' mirror made of quartz, coated to pass infra-red.
It was decided at this stage that all IMAX films must be printed on polyester (mylar) base, because although the Rolling Loop system accepted acetate prints, it did not take kindly to tape or cement joins. With polyester base the joins are ultrasonically welded and do not break even after thousands of passes. Also polyester does not shrink with age like acetate, a problem which could cause unsteadiness.
Quite apart from the projector a totally new camera was needed so that filming could commence for the Osaka Expo project. A Norwegian designer of specialised film equipment, Jan Jacobson, was chosen for this task, and he surprised everyone by having the first prototype available in only 3 / months. The Rolling Loop was not required for the camera which had a normal claw for pull-down, and a vacuum plate to keep the film flat during exposure. A mirror reflex viewfinder was incorporated, and a 1000ft 70mm magazine attached to the side of the camera, There was no camera blimp and so shooting with sync sound was not going to be possible. Standard Hasselblad lenses were used, ranging from 40mm to 600mm.
Much to everybody's surprise, including the Canadian Government, the team designed, built, and delivered their new projector on budget and on time, for the Osaka premiere of their film Tiger Child. IMAX was born, and became an instant success with 30,000 people a day clamouring for admission to the specially constructed Fuji Pavilion which resembled a bouncy castle!
The Osaka success was repeated the following year when the IMAX production team promised to deliver something spectacular for the 1971 opening of Ontario Place in Toronto, a sort of permanent 'mini' Expo on the lakeside, the centre piece of which was a giant spherical auditorium. Graham Ferguson immediately went to work shooting anything and everything which gave an insight into life in the Province of Ontario. He visited Indian Reservations, flew over lakes and cliffs, went white water rafting in a huge circular rubber inflatable, and was lucky enough to obtain some amazing footage of a large forest fire. The net result was a 25 minute documentary which he called North of Superior. This was the second IMAX film but the first one not to include multi images.
I was invited to mix the sound track at Film House, Toronto, which we decided would be 6 tracks reproduced on a separate 35mm magnetic film. Film House at that time had two 3-track re-recording theatres, so by purchasing a set of 6-track heads and using all channels we were able to get underway. The six tracks were designated left, centre and right behind the screen, rear left and rear right in the auditorium and the sixth track overhead. There were no Dolby units available in 1971, except one Dolby A unit which was 'On approval'.
Since there was no sync track to work with, only a small amount of conventional track laying had been carried out including music and some sound effects. For example the forest fire sequence was strangely silent! I will not dwell on the mix except to say that generous helpings of fire crackle loops fed into all channels worked wonders. I also had a helicopter on the overhead channel with a speaker announcement warning people to evacuate the area. Although this heightened the dramatics, I was instructed to remove the effect as it might make the audience get up and leave prematurely!
The day came when everybody retired to the 'Cinesphere' where the IMAX projector had already been installed. On top of the projection booth was a standard music mixing console for sound distribution from IMAX and other projection systems. My six tracks of audio were channelled into the available 57 loudspeaker systems and the impact of the huge screen and multi-channel sound was quite tremendous, better even than it sounded at Film House. In fact the film won the award for best sound in the 1971 Canadian version of the Oscar Ceremony.
When North of Superior opened the Osaka success was repeated with queues all day waiting to get in. Since then a large number of IMAX films have been made, and IMAX cameras have been co-ordinate space aboard NASA's space shuttle to bring back some remarkable pictures, A new film called Destiny in Space dealing with the repair to the Hubbell telescope is about to be released.
Mention must also be made of IMAX's twin, OMNIMAX, which uses the standard IMAX projector but with the picture projected on to the inside of a planetarium dome. The first Omnimax theatre in San Diego was an outstanding success, with an average attendance of 400,000 people annually. The projector is mounted in the middle of the seating area, and a 180 degree 'Fish eye' lens projects an image beyond the field of vision. Having witnessed Omnimax I think I prefer the straightforward IMAX system.
Early in January 1994, it was announced that the IMAX Corporation has been taken over by another Canadian company whose principal shareholders include Douglas Trumbull of 'Showscan', the 70mm at 60fps system, and leading merchant bank. Already there is IMAX 3-D where the audience dons Polaroid glasses, and IMAX HD running at 48fps. Digital sound on disc is now available as an alternative to the dated 6-track 35mm magnetic film, and a new Personal Sound Environment system about to be launched.
Currently the only IMAX theatre in the UK is at the National Museum of Photography, Film and Television in Bradford. If any member has not yet made the pilgrimage, I would recommend that they do as the experience will be well worth the trip. The British Film Institute has also applied for planning permission to build an IMAX theatre in the roundabout at the south end of Waterloo Bridge . It would seat 500 people, and once planning permission has been given construction would take 18 months.
Meanwhile Bill Shaw remains as a consultant engineer to the new consortium, and Graham Ferguson is concentrating all his energies on space films. It seems there is still a lot to do and a long way top go in refining the IMAX system.