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Recent British Equipment and Technique for High-Speed Cinematography*
BY G. A. JONES AND E. D. EYLES
RESEARCH LABORATORY, KODAK LTD., HARROW, ENGLAND
Summary — New British cameras for high-speed cinematography are described, among which are included those designed by Marley1 and by Brailsford and Shrubb.2 The principles of a new Kerr-cell electro-optical shutter which can be used for cinematography are outlined, together with details of its performance. New light sources for high-speed cinematography include mercury-vapor lamps run at high current densities, and foil-filled flashbulbs fired in rapid succession. Several applications of high-speed cinematography are described showing how the solutions to engineering problems have been obtained when the parts concerned are in rapid motion, especially when the amplitudes of the movements are too small to resolve easily in a normal record. The vibration characteristics of the anvil of an 8-ton dropforging hammer were determined by the use of a special optical system attached to the anvil. Because of the widespread disturbance caused by the hammer blow, an artificially fixed point in space for reference purposes was arranged by means of a long-period damped pendulum system bearing a fiducial indicator. The surface characteristics of white-hot steel bars were studied during high-speed rolling by means of high-speed cinematography using ultraviolet light.
DURING THE PAST two or three years, the use of standard ultrahighspeed cameras for investigational work in Britain has increased, and details have. been published of a certain number of highly specialized high-speed cameras. None of these has been aimed at exceptionally high picture frequencies, largely because experience has shown that even in ballistics work, a frequency of 100,000 frames per second is ample, while most ordinary industrial problems can be successfully investigated at frequencies of 3000 pictures per second or less.
In general, these cameras incorporate optical means of compensating for the movement of the film, which is in continuous motion, and the subject is illuminated continuously. Alternatively, the subject is illuminated by a series of flashes of short duration from a gas-discharge lamp, the flash frequency of which is controlled by a commutator coupled to the film-driving mechanism of the camera. A further refinement consists in using a combination of synchronized multiple-flash illumination and optical compensation for film movement.
* Presented April 6, 1949, at the SMPE Convention in New York. 502 NOVEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53