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XIII. PROJECTION AND PROJECTORS
Projector designs vary widely in performance with respect to flutter. The practical result is a rather wide range of flutter variation among even the present-day products of different manufacturers. As might be expected, the performance of the very best will leave something to be desired when compared writh the best current commercial 35-mm theater equipment. The performance of the very best is usually satisfying on most recorded music and on all speech for the average listener, although it may fall short for a critical listener such as a trained violinist who may be listening to familiar instrumental recordings. The SMPE test film previously mentioned is guaranteed to have less than 0.1%
FRONT TAKEUP BELT CROSSED
.SHUTTER /CONTROL
Fig. 110. Film path of old design machine with excessive flutter.
flutter when new. Some of the very best 16-mm machines may show as little as 0.2% flutter when new; however, the flutter in all machines is not equally disturbing at all frequencies. Good performance will show less than 0.25% flutter at rates above 25 cps, 0.15% between 25 cps and 1 cps. An increase in flutter at rates lower than 1 cps is not considered objectionable if it is inversely proportional to the square root of the frequency below 1 cps. It is doubtful than any commercial 16-mm projector meets all these requirements; should one do so by chance, it is doubtful that its performance would continue for any appreciable period due to the influence of machine wear upon flutter. The design of most 16-mm machines provides much room for improvement in the choice of materials and in roller and bearing design, together with a tightening of tolerances of the;.various parts of the film transport system. Such improvements could result in materially improved performance.