The art of sound pictures (1930)

SOUND TECHNIQUE 217 has dropped. This fact is due to a chemical physiological effect on the retina of the eye itself. The photo-chemicals of the retina have been changed by light from the object looked at. For a fraction of a second these little organs of the retina remain in their changed condition, and as long as they so remain, the individual will continue to experience the sight of the object which he had previously looked at. When a series of pictures such as those described are shown in rapid succession, the second picture in the series registers upon the retina while the image or trace of the first picture is actually present. Therefore, the person who looks at the two pictures in succession perceives no gap between them, and it looks to him as though the object or person looked at actually moved from one position to the next. Of course, in the early slot machines, the succession of pictures was comparatively slow. As a result, there was a noticeable pause between the pictures, which gave the effect of flicker. In the silent motion picture projecting machine, the successive pictures printed on a celluloid film are shown in much more rapid succession. This succession is so rapid that the person watching cannot observe the transition from one picture to the next. Therefore, there is no flicker or break between the pictures, and the total effect is one of natural movement of people and objects on the screen. In order to show successive pictures of movement, a correspondingly rapid successive series of pictures must be photographed by the motion picture camera. Mechanical devices were accordingly developed to draw the recording film rapidly past the lens of the camera, with a correspondingly synchronized device for opening