British Kinematography (1952)

June, 1952 STRANGE : DIMMING OF FLUORESCENT LAMPS 191 trated within 40 or less and an even illumination of the surround can be achieved with very little available depth. Automatic dim ming is now available so the linking of surround brightness with average screen brightness presents no great difficulty. REFERENCED Amick, G. L., " Fluorescent Lighting Manual," McGraw-Hill Book Company, 9, 1947. Strange, J. W., " The Dimming of Fluorescent Lamps and Its Application to the Theatre," Trans. III. Eng. Soc, 15, 111, 1950. " The Prize Remodelled at Gretna Green," Ideal Kinema, 18, 11, March, 1952. Pulman, R. E., " Screen Visibility in the Modern Picture Theatre," Light & Lighting, 44, 197, 1951. Hopkinson, R. G., Mackenzie, R. B. & Nixon, R. D. " Some Factors in Pictorial Reproduction Processes with Special Reference to Television," Phot. J. 91B, 2, Jan.-Feb., 1951. 6. Guth, S. K., " Surround Brightness : Key Factor in Viewing Projected Pictures," ./. Soc. Mot. Pic. & Tel. Eng., 57, 214, Sept. 1951 (reprinted Bnt. Kine., 20, 8, Jan., 1952). 7. Logan, H. L. " Photometric Factors in the Design of Motion Picture Auditoriums," Ibid 225. 8. Hopkinson, R. E., " The Lighting of Buildings," Light & Vghting, 44, 13, 1951. NEW FRENCH STANDARDS CINEMATOGRAPHY. Specification and methods of test for sound recording equipment. (NE) 528-001, Aug. 1951). The specifications include a section containing a number of general items of a mechanical or purely electrical nature, together with tests for susceptibility to magnetic fields and microphonic pick up. Amplifier tests comprise input and output impedance, gain at 1 kc, frequency response over the range 30-10,000 c.p.s., harmonic distortion, and noise level. The optical modulator system is tested for frequency response at modulation depths of 25 per cent, 50 per cent, 75 per cent and 100 per cent, using a calibrated P.E.C. monitor. Two alternative methods of flutter test are described for the camera mechanism ; a frequency of 3 kc. being used. Overall frequency response is measured at modulation depths of 20 per cent, 40 per cent and 80 per cent by recording test negatives and measuring same by microdensitometer. Photographic tests also cover noise reduction adjustment, volume range (signal/noise ratio), cross modulation, intermodulation and harmonic content. In presenting the test results, it is emphasised that adequate verbal description and diagrams be given, both of test procedure and findings. Response curves should be drawn using logarithmic scale of frequency for abscissal and decibel response of ordinates. An ordinate scale of 1 cm. to 5 db. is recommended for facilitating comparison of results, but curiously, no dimension is mentioned for the logarithmic frequency scale length ! It would seem that a fixed ordinate/abscissal ratio would be more helpful in comparing results. N.L. PHOTOMETRIC CALIBRATION OF CAMERA LENSES. (NE)S2S-002, Aug., 1951) The specification includes a description of the test apparatus, the method of use and recommendations as to calibration markings. An internally illuminated integrating sphere is used as a source, and the light transmitted through the lens under test illuminates an opal glass plate at the focal plane. The opal glass is fitted with a mask having a circular aperture of 2.5 mm. diameter, and the illumination of the glass is compared with that obtained when the lens is replaced by a standard mask of aperture f4. A tolerance of 7 per cent is allowed in the scaling, which is always to be read after adjusting the aperture ring to its settings in a closing direction. Photometric calibrations are distinguished by the letter T, and where the lens mount carries both geometric and photometric scales, the latter should be marked in red. N.L.