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Op timum Exposure of Sound Tracks on Kodachrome Films
By ROBERT C. LOVIGK
Low-distortion sound tracks on Kodachrome films can be obtained with any conventional exposure method. The best possible sound reproduction requires exposure with light of color quality which correlates the speeds of the individual emulsions when developed to silver sulfide rather than to dyes. Poor sound quality in the past has often been the result of the.failure to recognize the critical color quality requirement of the light which exposes the sound-track portion of the film.
.ODACHROME Duplicating Color Film, Type 5265 is a 16mm, reversal film designed to be printed from color positives on Kodachrome Films, Daylight Type (5263), Type A (5264), and Kodachrome Commercial Film (5268). The soundtrack deposit is silver sulfide. The soundtrack record is printed from silver positives prepared according to long-standing recommendations.
The sound process for Kodachrome films consists of three basic steps. First, the silver halides which were exposed in the sound-track printer are developed to a silver negative image. Second, thesilver halide which remains is converted to silver sulfide. Third, the negative silver is dissolved, leaving a reversal silver sulfide image.
There are many complicating factors
Presented on April 24, 1952, at the Society's Convention at Chicago, 111., by Robert C. Lovick, Color Control Div., Eastman Kodak Co., Rochester 4, N. Y.
in this basically simple process. For example, the necessity of confining the sound developer to the sound-track area within small tolerances precludes the use of agitation to aid in securing uniform development.
Recent studies have shown that a large part of the stain level of Kodachrome sound records results from conversion of some of the negative silver to silver sulfide. A modified developer which converts a much smaller part of the negative silver to silver sulfide is now being used. There is a small improvement of signalto-noise ratio which is the result of the increased useful transmission range. The sensitometric effect of the sound developer modification is shown in Fig. 1.
Standardized Printing Methods
Printing to obtain the best possible sound tracks on Kodachrome films requires consideration of three facts. First, the exposures are made on a multilayer film. Second, the three emulsion
August 1952 Journal of the SMPTE Vol. 59
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