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A. S. HOWELL AND J. A. DUBRAY [J. S. M. P. E.
plete change in the standard shape of the perforation could be made without extraordinary inconvenience to the industry.
The sound record is located, for all proposed dimensions, outside of the perforations, because it may be found advisable in future times, for economical and mechanical reasons, to use in the photographic camera negative films of a width narrower than that of the finished prints — a width sufficient to include only the picture record to the exclusion of the additional width of the sound record. This would be in accordance with the practice of photographing the sound record independently and with different apparatus than that used for photographing the picture record.
The placing of the sound record outside of the perforations has also the important effect of reducing to a minimum the distance between perforations and guide control rails, thereby providing better support for both the picture and the sound records.
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FIG. 4. Film support in regard to position of perforations.
Fig. 4 represents such a condition. Where the perforations are situated near the edge of the film, the film itself is unsupported for a greater length, as shown in the section, than is the case where the perforations are located nearer each other. It is quite obvious that the greater the gap between the two supporting points, the greater are the possibilities for the film to bend or curl out of the position of essential flatness, which must necessarily be kept within extremely small tolerances.
Up to the time of writing of this paper, it was quite evident that the sound engineers engaged in research and development activities were quite undecided and reluctant about expressing themselves with regard to the best arrangement for the sound record. This was evidently due to the complexities and the large number of factors involved in the problems which were presented to them for solution. It seems logical, however, to reach the conclusion that a longer sound record per picture area would permit the recording