Journal of the Society of Motion Picture Engineers (1930-1949)

372 ABSTRACTS [j. s. M. P. E. countercurrent flow. A convenient method of controlling the flow is one which takes advantage of the difference in density of the liquid at the last (film) stage and at the first where the bath is being diluted by developer carried on the film. If all the tubes are connected by small pipes at the bottom, the step-by-step change in gravity from one end of the machine to the other will cause a difference in liquid level from the first to the last tube. Although each tube is equipped with an overflow hole near the top, liquid will overflow only from the one or two tubes (of ten) nearest the developer because of the greater dilution with the consequent high liquid level. Thus the liquid is always discharged at the diluted (and exhausted) end. (In American practice where the water enters the fixing bath from a water rinse, this effect is also present. — Abstractor's Note.) C. E. I. Orthochrome Screen Eases Eye Fatigue. Mot. Pict. Daily, 29, January 20, 1931, p. 6. A description of a motion picture screen which regulates the spectral character and brilliance of the reflected light and thus is claimed to minimize eye fatigue. The surface of the screen is divided into a multiplicity of uniformly distributed areas, part of which are covered with a light filter, absorbing all or part of any predominant wave-length. A surface of uniformly distributed units results, each pair of which is claimed to reflect a composite of the wave-lengths, the sum of which presents to the eye white light or light to which the eye can react harmoniously and rationally. The nature of the filter chosen helps diffuse the light to reduce glare. G. E. M. Increasing Light Efficiency in Projection. F. HAUSER. Filmtechnik, 6, December 13, 1930, pp. 1-6. Tests of the Busch Neospiegel mirror reflector for increasing the efficiency of the projection arc show it to be superior to the ordinary spherical reflectors. The newly developed reflector is claimed to overcome some of the objectionable properties inherent in elliptic and parabolic shapes. The results of tests of new large-aperture projection lenses developed by the same firm are given. A large number of illustrations are used which show the benefits obtained with the various optical trains. L. E. M. Testing of Sound-Picture Channels. G. F. HUTCHINS. Electronics, 2, No. 2, February, 1931, p. 500. In sound picture production, it is important to have a complete knowledge at all times of the condition of each recording channel. This should be tested as a matter of daily routine and this paper is concerned chiefly with the details of these tests. A. C. H. Frequency Characteristics of Optical Slits. J. P. LIVADARY. Electronics, 2, No. 2, February, 1931, p. 512. An analysis is made of the attenuation due to the finite width of the slit in sound recording. A table is included showing the attenuation losses as a function of frequency for slits having a width of 0.5, 1.0, 2.0, and 3.0 mils. A. C. H. Sensitizing the Photo-cell. RICHARD FLEISCHER. Electronics, 2, No. 2, February, 1931. The sensitizing of photo-electric cells by means of a glow discharge in hydrogen has been known since the time of Elster and Geitel. This sensitizing process produces a marked increase in sensitivity and a shift in the spectral sensitivity. The constancy of a sensitized cell depends principally upon the establishment of a condition of equilibrium between the residual gas and the photo-electric