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62 CINEMATOGRAPHIC ANNUAL
The most ingenious method by which these serious evils were eliminated was originated in America by A. S. Howell, Chief Engineer of the Bell & Howell Company. He devised a cam actioned intermittent mechanism so designed that the moment in which the film begins its movement downward, or upward, as the case may be, all pressure upon its surface is removed and the film is allowed to run freely through its channel. Pressure is again applied as soon as the film is in its stationary position, while perfect registration is secured at this exact moment by a pair of closely fitting stationary registering fingers which engage into a pair of perforations.
From the early days of Cinematography, it has been possible to reduce the speed of the camera at will and according to the needs of the operator. We all remember the beautiful results obtained by Pathe Freres in their educational pictures showing the growth of plants, the budding and blooming of flowers. Each picture frame was taken at seconds or minutes and even at hours interval and the film projected at normal speed showed in a few seconds the work that nature took days to perform.
Stop motion photography and reduced speeds in the taking of the photograph record were also very extensively used in films for entertainment; and very few comedies were made in the early days which did not, at some time, take advantage of the comical effects that can be obtained through this simple medium.
But the need was also soon felt for a camera which would permit a more exact analysis of motion of subjects moving at a great rate of speed. This demanded the recording of a much greater number of picture frames per second than the normal of 16, so that when projected normally the speed of the subject would be reduced proportionally to the higher speed of recording.
This phase of motion pictures interested at first only the research laboratory, and France lead the way in this field. As early as 1910, at the Marey Institute of Paris, as many as 2000 pictures per second were obtained with a camera in which a continuous movement was imparted to the film and the effect of intermittence was obtained by rapidly extinguishing and exciting a source of light. To obtain this effect, rapidly succeeding electric sparks were used and their frequency was secured by means of a current interrupter synchronized with the film driving sprocket.
Pictures at such high frequency (as many as 25,000 pictures per second have been obtained in laboratory experiments) had very little use in commercial cinematography, but it was soon evident that high speed cinematography could be used to great advantage in miniature cinematography, that is to say, for scenes in which the speed of objects of natural size was to be brought into time with the ambient of reduced size in which those objects were moving.
M. Labrely, of France, to whom ultra speed cinematography is greatly indebted, designed a camera with an intermittent movement, which could, with relative ease, take as many as 100 to 150 pictures per second. This camera was used in the first slow motion pictures presented to audiences in public auditoriums by Pathe Freres. The