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THE OPTICAL LANTERN AND CINEMATOGRAPH JOURNAL.
with a coating of gelatine dry-plate emulsion of the most rapid nature possible. Each picture is about the size of an ordinary postage stamp, and the strip of film is perforated on the edges (see Fig. i). The purpose of these perforations is to provide means of
passing the film through the camera during the taking of the pictures. Thus the teeth of the procket wheels pass into the perforations and drag the film forward in their motion. By means of the procket wheels and the supplementary mechanism, the film is carried through the camera at a rate of one foot per second. A rotary shutter is made to revolve between the lens and the film sixteen times per second ; and whilst the shutter covers the lens the film is passed one space forward, remaining stationary whilst the lens is uncovered and the exposure is being made.
Some cameras are provided with detachable magazines for holding the film; whilst others are designed with the magazines contained in the body of the camera ; the latter pattern being more convenient when travelling across country. The chief points of importance in the photographic camera for animaphotography are — (i) A good lens that will permit of a large aperture being used, so that in dull weather as much light as possible may be emitted to the film ; and this without sacrifice in definition of the image. (2) A rotary shutter that may be adjusted for varying lengths of exposure. (3) A changing device that is certain in its action of passing on the film, without scratching the gelatine or tearing the perforations ; and also of passing the film with equal spacing throughout.
The speed at which the pictures are generally taken is about 16 per second. As far as final results upon the screen are concerned, the larger the number of pictures that are projected per second, the better will be the impression produced ; for it will be more continuous, and with less flicker. Unfortunately, however, the atmospheric conditions when the negative is taken will not always permit of such rapid exposures as one might desire.
If it were possible to take a hundred pictures per second, instead of the normal sixteen ; and at the same time to secure such pictures with full density and definition ; when the positive therefrom was projected at an equal speed upon the screen, which, by the way, would envolve a much more powerful illuminant than is usual the effects would be practically flickerless and very natural. But this being as yet both a mechanical and chemical impossibility, we must content ourselves with making the best use of the means at hand ; using in most instances the fastest film emulsions ; choosing the most perfect and rapid optical combination ; and exercising a
Fig. 1.