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T 1 I E C I N E T E C H N I C I A N
Jan.— Feb., I98fl
THREE THOUSAND PICTURES A SECOND
by D. H. GEARY
HERE is ;i marvellous creation of British camera engineering skill — a slow motion camera that w ill take 3,000 pictures a second. Constructed by Vinten, the camera is carrying out important investigations at a Government establishment, and two further models have been built. The camera was designed purely for research purposes, although it has its uses for documentary films. The enormous film speed precludes the use of any form of intermittent motion, and therefore the film must run continuously. In front of the gate is a duralumin ring, perfectly balanced, and mounted in this ring is a series of 48 matched lenses. The lens ring is geared to the film traction apparatus so that the peripheral speed of the axes of the 48 lenses is the same as the linear speed of the film. It will be seen from this fact that when the film and any given lens come opposite to the light aperture in the gate, the film and lens are relatively stationary. By this method full advantage is obtained of all light reflected from the object to be photographed.
Between the film and the lens ring is an adjustable slit which acts as a variable shutter. The lenses employed are of 2in. focal length with an aperture of f 3.5.
The focus is set at infinity by adjusting the position of the gate in respect to the lens. In order to enable the operator to photograph objects at any distance from three feet to infinity, a series of auxiliary spectacle lenses arcsupplied. These are marked for the various distances required, such as 58 inches. tOOin., 200in., and so on.
These auxiliary lenses are inserted in a slide in front of the lens ring. It is obvious that as simple a film path as possible must be employed, so it is necessary to have large openings in the magazines. The magazines accommodate 400 feet of film and are so constructed that they must be in a closed position before the camera can be opened or closed. Owing to the high speed of the mechanism a special form of lubrication has been devised, b\ means of which oil is inserted to all moving parts under pressure. Of course, special precautions are taken to prevent the oil coming into contact with the film. It is also important to forecast the results which might
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