A Simplified Distortion Balance Test Procedure for Optical Sound Records and Prints

A brief review is made of the sources that introduce distortion into the recordings of optical sound on film. One is the aperture (slit) width of the sound recorder, which may cause amplitude distortion and rectification effects. Other sources of distortion are light scattering in the negative emulsion, variations in process sensitometry, and other process and photographic sources, such as the Eberhard and Ross effects, and the individual characteristics of specific photographic materials and processes. A delicate operation is the transfer of the information contained in the sound record negative to the print film. Causes of distortion during the transfer phase are discussed. Next, distortion balance methods, that is, methods for the correction or cancellation of distortion, are enumerated. A new and simplified method for obtaining distortion balance is described in detail. This method is based on the light-spot scanning of peaks and valleys at selected ordinate distances from the zero axis of the soundtrack. It is intended for evaluating the photographic materials without interference from other elements of the sound recording system, such as the recorder, the printer, and the sound reader. The functioning and application of the new method is described in detail. Experimental data show that this new method correlates well with the conventional cross modulation method, but is much simpler and easier to incorporate into the customary sensitometric control routines of a motion picture processing laboratory.

Print ISSN

0036-1682

Published

1981-02

Content type

Original Research

DOI

10.5594/J01498