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A PRINTER FOR SIMULTANEOUS PRINTING OF SOUND AND PICTURE NEGATIVES
Oscar DePue*
THE printing of sound pictures on a rapid basis is, of course, only possible by a continuous machine, and the possibility of a rapid continuous machine being used has been greatly enhanced by having a suitable automatic light control. This, we believe, is the advantage of the machine we are trying to develop over a slower method of manual control or a limited automatic control. The fact that both sound tract and picture printing light should be controlled by automatic means gives our very large capacity, automatic control a chance to demonstrate its worth in the art.
Moving a negative past a narrow aperture was the very first means employed by the writer in printing positives as early as 1897, when a 60 mm. film was used. To compensate for the shrinkage and the holding of these two films in contact, two sprockets were employed, geared together, the negative sprocket being a trifle smaller to allow for the difference in shrinkage. The control of the lighting, however, at that time was unheard of so far as the automatic means was concerned. The method used was to move the light backwards and forwards to correspond with the different densities which, of course, limited the speed of printing. The automatic change by resistance, which we are now employing, has stood the test for over ten years in our work, as applied to a continuous movement past a narrow aperture. In fact, the combination is a good one, as the continuous movement and the comparatively gradual change of illumination from weak to strong, or reverse, spreads the change of light over a sufficient distance on the print to give the effect of a fade-in or fade-out, as it were, and no rapid or abrupt change takes place in one or more frames of the print.
One of the important features of a printer of this kind, we have found, is that the printing should actually take place just as near as possible to the point on the sprocket wheel where the film is striped from the teeth. We have also found that the size of the sprocket wheel is very, very important. We worked at first on the * DePue and Vance, Chicago, 111.
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