CHAPTER VIII
ABERRATIONS OF ANIMATED PHOTOGRAPHY
It has been pointed out in a previous chapter that cinematography is nothing more or less than an optical illusion. Further proof of this assertion exists in plenty. When following the projection of a picture upon the screen, one is often perplexed by a curious effect, or a movement which appears to be in opposition to all the known laws of motion. This happens not only in trick work where such odd and startling effects are introduced purposely, but in straightforward every-day topical subjects.
For instance, it must have been noticed that when a ship or railway train is in rapid movement, and is photographed from a fixed stationary point, such as the quay or platform, the moving object appears to stand out in bold relief against the background. One gathers a very comprehensive idea of its length, width, height, and the comparative size of all its integral parts, such as the guns on the ship's deck or the locomotive's cylinders. It is a curious stereoscopic effect, but at the same time is not truly so, because it is only the moving object which appears to possess solidity. The foreground and background remain as plane surfaces so that it is impossible to obtain an idea of distance. This effect arises from the fact that what might be described as the central part of the picture is moving or continually changing, thereby compelling all the objects attached to its length and breadth to assume relief in regard to the other parts of the picture.
But if the camera with which the pictures are taken is placed upon the moving object itself, then the whole of the resulting picture stands out in a truly stereoscopic manner. One gathers an impression of distance between the various objects on the screen. Everything is shown with form and solidity in precisely the same way as if one were looking through a hand stereoscope upon a photograph taken stereoscopically. This effect is due to the fact that all the planes are moving continually.
But probably the most bewildering puzzle is the moving wheel. A carriage or waggon is seen advancing across the screen from left to right, but the spokes of the wheels, on the other hand, seem to be moving in the opposite direction. At other times the spokes move in successive spasmodic jumps, or appear to be stationary, so that a curious skidding effect is produced, notwithstanding that the rim itself is seen to be revolving normally.
There have been many explanations of this extraordinary effect, and in one instance the higher mathematics were pressed into service without any great success. The most convincing explanation known to the writer is that given him by Monsieur Lucien Bull, the assistant-director of the Marey Institute, where phenomena of this class are minutely investigated, because they accord with the work of that unique and admirable institution. By Monsieur Bull the illusion was explained very easily, but, curiously enough, in carrying out the experiments to this end, he encountered another illusion equally strange.
