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Misc Film
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70mm film with six magnetic sound tracks
Note 5 perforations per frame, not four as used on standard 35mm films
Two sound tracks are on the large stripes on each side, and one track on each of the inside stripes
The small round holes are to show the projectionist the correct way round to lace the film
These should be away from you when lacing up
The six sound tracks fed signals to the five sets of speakers behind the screen, and the sixth track fed the surround speakers in the auditorium
The five speakers behind the screen were designated outside left, inside left, centre, inside right, and outside right
Magnetic sound has now been superceded by DTS digital sound
The making, and striping, of mag tracks has been deemed to be environmentally unfriendly
The Early 70mm films, Oklahoma, South Pacific etc, ran at a projection speed of 30 frames per second
This was mainly to produce superior sound reproduction, but as sound equipment, recording, and play back progressed, and probably to save money
on film stock, 70mm films were filmed, and projected at the normal speed of 24 fps
Now, 35mm runs 90 ft per minute at 24fps, but 70mm at the same frame rate runs at a speed of 112ft 6ins per minute
This is because the frame is of five hole height, and not four hole as found on 35mm
Therefore the speed is increased by 25%
Plenty of running around by projectionists when using changeovers
The invention of the platter (cakestand) was a godsend
The picture quality easily outstrips any digital picture to date
70mm is truly High Resolution
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