International photographer (Jan-Dec 1941)

16mm. dEPARTMENT Some Fundamentals Underlying Sound-on-film The average amateur either is of insufficient affluence or feels that the making of a sound picture is way beyond him. Consequently today there are few people doing any work with film where sound is employed. It is a fact that it is more expensive than straight photographic work, although not of sufficiently increased proportions to warrant ruling it out entirely. It also is true that it is more exacting than straight photographic work, but we feel that the amateur who has the ability to master his camera medium to the point where he can intelligently make pictures with it can do the same thing with the expanded equipment fulfilling the requirements of sound-onfilm. And since in recent weeks we have been confronted by several who have expressed an interest in the medium and wish to know "what it is all about," even though they may not engage in the actual production themselves, we are going to give them some of the basic fundamentals underlying its operation. In the early days of sound pictures, the sound was recorded on a disc, one similar to the phonograph records with which we are all familiar, but differing in that they were 16 inches wide instead of 10 or 12, and turning at 33% revolutions a minute instead of the usual 78. The recording was made in "sync" with the picture and started that way when projected — but often didn't remain that way through the entire reel! We are mentioning this particular method because we feel that manufacturers are overlooking a good bet for the amateurs. There are "home recording" machines available on the market today that retail for surprisingly small cost, are portable and easy (or relatively so) to carry, and above all use the very inexpensive acetate discs for the recording — which requires no processing. THE ONLY REQUIREMENTS THAT WOULD HAVE TO BE MET ARE THOSE OF SYNCHRONISM, and possibly an amplifier having greater ability to amplify or pick up weaker sounds than the present machines do and which doesn't present any particularly great problems. The maintenance of "sync," too, is no great problem, requiring only that a synchronous motor be used on the recorder instead of the usual "wild" motor, and the use of a similar "sync" motor on the camera instead of relying on the spring motor so prevalent on amateur equipment. Anyone who is familiar with the basic simplicity of the requirements involved here will agree that the one big expense has been entirely removed by the use of the acetate discs which sell for about ten Actor and Cameraman Confer John Carradine, quite an amateur photographer, ami Arthur Miller discuss the next camera set-up on Twentieth Century Fox sea set of "Son of Kurv." or fifteen cents a disc and can be played immediately after recording, without processing. With proper care and use I by having a very light crystal pick-up) they will last. Such a combination is not only possible and feasible, but would open up an entire new field for the amateur that formerly has been closed to him because of the added cost of sound on film and the additional technical problems its use poised. It is our opinion that here lies a virgin field for a manufacturer and one that should prove as lucrative to him as it would be interesting to the user and it would open up for the amateur the possibility of making sound pictures. Of course, it should be emphasized that sound-on-disc is not as a flexible from the editorial standpoint as sound-on-film, but with a little ingenuity the amateur, who generally leads in advancement in almost any field, should be able to fit his technique to suit the medium and get some very satisfactory results. It must be added that the turntable on which the record is reproduced must also possess a "sync" motor, but with most machines on the market today there is also a pick-up arm that swings into place on the same table used for the recording, so there is no particular problem with the reproduction. But we started out to talk about soundon-film. This method of recording is a photographic process. Everything is done from a photographic standpoint; the little hills and valleys — or the varying intensities of light and shade I depending upon the system used ) are actually photographed pictures of vibrations as they are picked up by the microphone. On that premise let us proceed. Those of you who have studied physics will know that a sound wave is a longitudinal wave as opposed to the transverse nature of a light wave. In everyday language it means that the sound wave travels in a straight line and reaches its goal, our ears, by setting up a succession of minute disturbances in the air which alternately compress it slightly one instant and the next instant cause there to be a slight vacuum. // is this series of "condensations and rarefactions," as these compressions and vacuums are called, that represent a sound nave. If we strike middle "a" on the piano, the strings will vibrate at a frequency of I 10 times per second. That means that the air will be alternately compressed and then rarefied at the rate of 440 times per second. When this mechanical disturbance of the air reaches the microphone, these compressions— or condensations — and rarefactions — or minute vacuums — they set up a mechanical vibration in the sensitive portion of the microphone which will move about in any manner the sound waves happen to 20