Cine-film projection : a practical manual for users of all types of 16-mm. and narrow gauge film pro (1952)

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film flat upon its surface, and others smooth out the difference with the rest of the film by means of resilience. (Fig. 7). In one well-known projector the system of rollers is called the Oscillatory Stabiliser, an excellent description. If any part of this system becomes faulty a variation in the FILM PULLED BY TAKE-UP SPROCKET THROUGH SOUNDHEAD SCANNING SPRJNG IDLER. ROLLED FLYWHEEL ROLLER FOR CONSTANT SPEED Z+- FILM LOOP PfcESSUHE ROLLER. "DAMPING"FILM AGAINST SOUND DRUM. SOUND DRUM Fig. 7 4 DAMPING ' A pull-through type of soundhead without sprocket-wheel. speed of the film passing through the sound-head may result, and this will cause an unpleasant "wow" from the loud-speaker. Correct sound-speed must always be maintained, as any increase or decrease in the speed will result in the sound becoming sharp or flat respectively, and in much the same man- ner as the gramophone when its speed is altered. Should a sound-projector be run at silent-speed then the resulting sound will be terribly flat, as the silent speed of 16 frames per second is much too slow for perfect reproduction. All rollers in the smoothing system must be kept absolutely clean, and those fitted with a spring must be at just the right tension. Some rollers may have to be held back when threading the film, but care must be taken not to allow them to fly back into position, otherwise the sudden pull on the film will result in the sprocket holes becoming strained or torn. It should be noted that in some projectors these rollers do not require oiling, but instead are to be clean and highly polished. 41