American cinematographer (Jan-Dec 1935)

14 American Cinematographer C March 1935 Fig. 1. A general view of 16mm sound and picture recording camera. IN THE earlier stages of 16mm sound-picture progress, the larger part of the research was concentrated in the development of sound-on-disc equipment. However, the bulk and weight of such apparatus, coupled with the difficulty of securing proper synchronization between the disc and the film, turned this interest toward a soundon-film system. A combination of sound and picture on the same strip of film was then proposed to secure exact synchronization and to reduce the bulk of the entire equipment. At first, those engineers who were involved in the realization of such a scheme found themselves confronted with the seemingly impossible problems of design, weight, cost, dependability, and simplicity of operation of such apparatus. Despite all the unfavorable comments and predictions, most of these problems have been solved one after the other. At the present two important and distinct methods are used in producing 16mm sound-on-film pictures. In the first, sound and picture are recorded simultaneously and directly on a single strip of film by means of a specially constructed 16mm recording machine. A general view of such a camera with its auxiliaries, built by RCA Victor Company, is shown in Figure 1 . In the second method, 16mm prints are made from the existing 35mm films using either re-recording or optical reduction of sound. This article will present a discussion of the latter of these two methods of producing substandard sound-on-film pictures Optical Reduction of Picture and Re-Recording of Sound One of the two principal processes of preparing 16mm sound-on-film pictures from existing 35mm films consists in recording the sound and photograph on a 35mm nega Methods of tive and preparing a positive print from it in the usual manner. The picture of this print is then reduced by optical reduction and its sound track is re-recorded onto 16mm film. The final 16mm positive film is obtained using the reduced picture and re-recorded negatives in certain printing processes which will be explained below. According to the standards adopted by the Society of Motion Picture Engineers the dimensions of the standard 35mm sound film camera aperture are 0.368 by 0.631 inch while the corresponding dimensions on the standard 16mm sound film are 0.410 by 0.294 inch. Computing the reduction ratios in the two directions, it will readily be seen that different optical reductions are required in the horizontal and the vertical axes. Due to the introduction of such a difference in reduction ratios it is necessary to use a special optical system employing cylindrical lenses. Furthermore, as the gap between successive picture frames in the standard 35mm sound film is 0.117 inch and the corresponding gap in the case of the standard 16mm sound film is only 0.006 inch, which is only a very small fraction of the first, it is not possible to make use of the continuous optical reduction printing when a dupe • duplicate) negative is not available. For this reason a specially constructed printer is devised, known as stepprinter, which prints the optically reduced picture on the 16mm film frame by frame. The re-recording of the sound on 16mm is very similar to the original recording of sound on standard film, and is accomplished by a recorder which closely resembles a reproducer. A light ray, traversing the already recorded sound track of the standard film, produces light variations corresponding to the variable densities or variable areas of the sound track. These light variations falling on a photo-electric cell create electrical impulses which in turn are transformed to light variations by means of a glow lamp. The alternating optical exposures so produced leave impressions of a new and reduced sound track on the 1 6mm film.1 The optical reduction of the picture area and the rerecording of the sound track are usually made on separate strips of films. If the two operations are impressed on the same ribbon of film, a master 16mm sound-on-film is obtained. Continuous Printing of Sound and Picture The 1 6mm master negative carrying the comb'ned picture and re-recorded sound, or the separate picture and