British Kinematography (1950)

Feb., 1950 59 TECHNICAL ABSTRACTS Most of the periodicals here abstracted may be seen in the Society's Library. THE PHYSICO-CHEMICAL BASIS OF TRICHROMATIC IMBIBITION PRINTING. A. V. Bromberg and O. S. Maltzeva. Abridged in Sci. et Ind. Phot., June, 1949, p. 232. An extensive experimental treatment of dye-transfer printing from matrices dealing with : (1) Swelling of a gelatin layer ; (2) Dyeing the gelatin with organic dyes ; (3) Transference of dye. G. I. P. L. HIGH INTENSITY FLASH TUBES G. Knott, Phot. J., 89b, May-June, 1949, p. 46. HIGH SPEED FLASH TUBES AND THEIR APPLICATIONS. A. J. Meadowcroft, Ibid, p. 51. The first of these two papers describes the design factors which affect the light output and performance of electronic flash tubes. Curves show the characteristics of discharges in xenon, krypton and neon over a range of pressures and with tubes of various lengths. Data on standard tubes are given and special tubes intended for high speed photography and foF stroboscopic work are described. The delay in triggering is also discussed. In the second paper the principles of operation, and characteristics of a range of commercially available electronic flash tubes, are described. Their performance and characteristics are discussed, and photographic applications are mentioned. H. K. B. RECENT DEVELOPMENTS IN HIGH INTENSITY VAPOUR DISCHARGE LAMPS. E. H. Nelson, Phot. J., 89b, MayJune, 1949, p. 54. This paper outlines the physical properties of a discharge in mercury vapour at high pressures and describes the development leading to the compact source lamp in which a brightness of up to 100,000 candle per sq. cm. may be obtained. The paper also describes the precautions necessary for operating mercury vapour lamps. Highly loaded mercury vapour lamps give a reasonably good spectral distribution, particularly when cadmium is introduced into the bulb. The high power mercury cadmium compact source lamp gives good colour rendering in Technicolor. H. K. B. THE GAS ARC— A NEW SOURCE OF LIGHT FOR PHOTOGRAPHY. H. W. Cumming, Phot. /., 89b, May-June, 1949, p. 58. The gas arc is the name given to a discharge between two electrodes in a quartz tube filled with xenon. The tube is mounted in a jacket through which water flows to cool the lamp. The chief features of the lamp are that it will give full light output immediately after striking, and that the colour of the radiation is closely similar to that of daylight. A high voltage impulse is required to ignite the arc. As the lamp is water-cooled the heat radiation is extremely small. Its luminous efficiency, however, is only 25 to 30 L/W and its brightness is low. H. K. B. A HIGH INTENSITY LIGHT SOURCE FOR HIGH SPEED KINEMATOGRAPHY. E. J. G. Beeson, Phot. /., 89b, May-June, 1949, p. 62. Methods for producing the very high light intensity required for illumination in high speed kinematography are described. In one method a number of flash bulbs mounted on a disc, revolve in turn in front of a parabolic reflector and ignite as they pass through the focal position to produce a long flash. Incandescent lamp and carbon arc spotlights may also be used, although these introduce heating difficulties. A method superior to those available hitherto consists of flashing a mercury vapour lamp at a very high overload. For example, a 1 kW. compact source mercury cadmium lamp may be flashed at 10 kW. for 1 second, 5 kW. for 2 seconds or 3 kW. for 5 seconds. The colour of the radiation from the lamp is good. The characteristics of the lamp when used in this manner are described in detail. H. K. B. .