A Dynamic Check on the Processing of Film for Sound Records

The limitations of the sensitometric method of controlling film development as actually affecting the sound recording are reviewed. An auxiliary test designed to check the quality of the development technic is outlined. In this test, the over-all photographic process, including the light-valve circuit which controls the exposure of the negative, and the photoelectric cell which receives the current impulses in accordance with the transmission of the positive film, are considered as an electrical unit. This unit is analogized to a transducer in an electrical transmission circuit and, as such, its fidelity of transmission can be determined by comparing the electrical output with the electrical input. In practice this is accomplished by applying a constant amplitude of electrical input to the light-valve circuit at values of valve spacing selected to allow the peak exposures to extend to the limits of the exposure regions that are to be used in the recording. The resultant projected levels for each value of valve spacing are measured with a volume indicator on the projection amplifier. If the readings obtained are all the same, true reproduction over the exposure range used is indicated.

Print ISSN

0097-5834

Published

1935-08

Content type

Original Research

DOI

10.5594/J05389