The Cine Technician (1943 - 1945)

48 THE CINE-TECHNICIAN March— April, 1943 Edited by A. E. Jeakins TECHNICAL ABSTRACTS Mass Radiography in Industry — (British Journal of Photography, April 17th and October 30th, 1942). This brief account of the method used in mass radiography of the chest for diagnosing pulmonary tuberculosis is interesting, particularly as the Government has stated that mass radiography of the lungs of workers in industry is to be applied in a number of centres. The method consists in what is called indirect radiograph}', in which a miniature camera, is used to photograph the image of the patient's chest thrown on the fluorescent screen by the X-ray tube. The resulting miniature photograph is then projected to give a life-sized picture which is easily examined. Experience has shown that about 120 cases an hour can be comfortably dealt with. A distance of 36" is used between the X-ray tube and the screen. The miniature camera is about 35" from the screen. An 1.5 lens of 2" focus has proved satisfactory. The camera is joined up to the fluorescent screen by a light-tight tunnel and exposure is made by switching on and off the current feeding the X-ray tube. The only camera adjustment is the moving of the film between' exposures. Exposures of between 0.3 and 0.45 sees. (30 to 45 milliampese seconds) on Ilford H.P.2 film have given good results with thousands of subjects. X-Ray Motion Pictures — (Jerry Fairbanks, International Photographer, May. 1942). The author describes how the difficulties of photographing in motion the X-ray image on a fluorescent screen were overcome. Exposure and tube life were the main problems. The fastest 50 mm. coated lens available was used.. Eastman Kodak supplied a special 35 mm. filnrwith X-ray emulsion and spooled in motion picture lengths. The intensity of light necessary to make an exposure on the film produced a degree of heat thai caused the X-ray tube to collapse. A solution was found in the recently perfected rotating-anode tube, which operates at 100,000 volts and 500 milliamps. rl'he tube could only work at this intensity for a few seconds at a time. To extend this period of time long enough to make motion pictures a circuit braker synchronised with the camera shutter was used, so that the X-ra\ tube was off and resting during the film change period, and was accordingly able to supply a high radiation over a longer period. The film was protected from fogging b\ the X-rays by special lead-lined containers. New 16mm. Sound Camera— (Wm. stub. A.S.C.. American Cinematographer, April, 1942). In the U.S.A. where 16 mm. is being widely used in the production of training and defence films, the E.M. Berndt Corporation have put on the market the Auricon 16 mm. Sound Camera to serve as a companion to their successful 16 mm. Auricon Recorder. The new camera may be used alone for single-system sound and picture recording or interlocked with the Auricon recorder as a double system unit. The camera is of box form. The case, made of wood and lined with foam-rubber sound insulating material, does the double job of acting as a blimp as well as a carrying ease for the camera. The operating mechanism, built of tool steel, with precision cut gears and sprockets, is mounted on a heavy steel frame-plate inside the case and suspended on vibration-damping mountings. The film moving mechanism is of the single claw, pressure plate type, and it is claimed gives registration only surpassed by the best pilot-pin design. Recording is done at the main driving sprocket, which is fitted with precision cut teeth and a heavy fly wheel. The motor drive is of an ingenious and unconventional type. A small highspeed (1800 R.P.M.) synchronous motor is employed to drive the camera mechanism and a separate non-sync motor is used to power the take-up, governed by the smaller main driving unit. The motors operate on 60 cycle 110 volt current. For field use the unit may be driven from a battery fed portable power unit. The camera has a 200 foot film capacity (using standard daylight loading spools). Lenses from most Filmo 70, Bolex or Victor cameras may be used with the Auricon camera, as it is designed to take any type-C lens mounting. The finder is the simple open-frame type. Parallax correction is obtained by lateral adjustment of the near eye-piece along a calibrated scale. The forward frame is fitted to take cut-out mattes of coloured celluloid. The sound is variable area. The recording galvanometer is of rugged design, capable of taking considerable overloads. All the adjustments to the optical system are made at the factory and locked permanently in position. The frequency response of the system is stated to be greater than the reproducing range of most standard 16 mm. projectors. The amplifier is a separate unit. It makes use of the type of batteries and low-drain tubes used in most portable radios.