The art of sound pictures (1930)

2i8 THE ART OF SOUND PICTURES and shutting the camera shutter in front of the lens a specified number of times each second. In the old style of motion picture camera, the film was moved past the lens by hand. A spool of undeveloped negative would be inserted into a portion of the camera called the magazine. It would then be threaded in such a way as to pass across the lens to another spool in another portion of the camera, just as kodak film is fastened to a winding spool in amateur kodaks. The photographer would then wind the film on the empty spool or reel by means of a crank which he turned by hand. Thus, the speed at which the film passed in front of the lens was always somewhat variable, and the whole operation required long experience and training on the part of the camera man. The modern motion picture camera winds the film inside the camera by means of an electric motor which is automatically regulated to wind the film at the rate desired. This requires the operator only to set the motor at a given speed. All this sounds complicated enough. But it is simplicity itself in comparison to the additional process involved in shooting sound pictures. Here, the sound itself is photographed on what is called a sound track at the edge of the film. You can see at once that this necessitates the addition of a new and extremely complicated set of apparatus to catch the sounds of voices, music, and other noises, translate them into rays of light, and then register the light rays on the edge of the moving film properly synchronized with the pictures that are being simultaneously registered on the same film. The electrical and mechanical principles of this new sound photography can be made clear without going into