Journal of the Society of Motion Picture Engineers (1930-1949)

Record Details:

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Feb., 1930] CHARACTERISTICS OF SOUND FlUVf 187 In Fig. 2 and Table II are given data relative to the characteristics of Reprotone B film, a material developed particularly for use in sound recording by the light valve method. The characteristics of this material are very similar to those of motion picture positive with the exception of rate of development and the maximum attainable contrast (ya). An inspection of the time-gamma curve in Fig. 2 will show that it rises much less steeply and obtains an ultimate value REPROTONE. PEVEUDPER f\Q PEVELOPMENT VN MINUTE!, TIME LOG EXPOSURE 3.0 1.0 1.0 2.0 4.0 FIG. 2. Sensitometric curves for Reprotone B developed in metol hydroquinone borax. appreciably lower than that for the regular motion picture positive film. It is considered that this represents a desirable factor in material for this purpose. As stated previously, it is necessary to stop development when gamma reaches approximately 0.6. In the case of positive film the rate of change of gamma with time of development at this point as represented by the dy/dTd is 1.48, while for the Reprotone B material the value of this factor for the same contrast is only 0.65. This means that at the time when it is desired to stop