British Kinematography (1950)

24 BRITISH KINEMATOGRAPHY Vol. 16, No. 1 TECHNICAL ABSTRACTS Most of the periodicals here abstracted may be seen in the Society's Library. PHOTOGRAPHIC GRANULARITY AND GRAININESS. L. A. Jones and G. C. Higgins, Sci. et Ind. Phot., June, 1949, p. 201. A new concept of granularity measurement is introduced based on the realisation that graininess is perceived by virtue of a scanning process carried out by the eye on the granular deposit. W. F. B. THE BRIGHTNESS OF THE SURROUNDING FIELD AND ITS INFLUENCE ONCORRECT SUBJECTIVE REPRESENTATION (OF PICTURES). J. Eggert, ScL et Ind. Phot., June, 1949, p. 204. The author demonstrates that pictures should be viewed with a surrounding field the brightness of which corresponds to that which one would expect to find in a similar field under naturally occurring circumstances. W. F. B. USE OF TEST FILMS G. Lechesne, Tech. Cine., May 31, 1948, p. 118; June 30, 1948, p. 147. A series of 35 mm. test films, standardised by the Comite Technique du Cinema, comprises films for checking picture steadiness (having holes in the frame area punched at the same time as the perforations — also available for 16 mm.) ; for centring the projector on the screen ; for detecting picture distortion by means of a grid ; buzz-track, frequency films, and warble-tone tracks. Methods of measuring screen brightness are also specified. R. H. C. PRE-SELECTION OF VARIABLE-GAIN TUBES FOR COMPRESSORS. Kurt Singer, J. Soc. Mot. Pic. Eng., June, 1949, p. 684. The procedure described includes the use of a valve matching circuit in which an alternating test voltage is applied in phase to the two signal grids of the pair of valves under test, and the out-of-phase voltage at their anodes is measured. The test is carried out both for small inputs at zero bias and also, by means of a rectifier clamp circuit, for large inputs under dynamic, or self-biassed, conditions. N. L. ZERO-SHIFT FOR DETERMINING OPTIMUM DENSITY IN VARIABLE-WIDTH SOUND RECORDING. C. H. Evans and R. C. Lovick, /. Soc. Mot. Pic. Eng., May, 1949, p. 522. The authors describe a method for the direct measurement of envelope distortion by comparing the mean densities of modulated and unmodulated tracks. The apparatus required is relatively simple and only a minimum of film is required. Results, if proper precautions are taken, are found to agree well with the more usual cross-modulation tests. M. V. H. THEATRE LOUDSPEAKER DESIGN, PERFORMANCE, AND MEASUREMENT* J. K. Hilliard, /. Soc. Mot. Pic. Eng., June, 1949, p. 629. After discussing the scope and purpose of loudspeaker testing in relation to design, the author describes the technique of open-air free-field measurement. Examples are given illustrating tests for phasing, balancing of multi-way systems, impedance matching frequency response and harmonic distortion. N. L. THEATRE TELEVISION SYSTEMS. Richard Hodgson, /. Soc . Mot. Pic. Eng., May, 1949, p. 540. The apparatus in the Paramount Theatre, New York, employs the intermediate film principle by which the television programme is recorded on 35mm. film from the picture on a cathode-ray tube, and after rapid processing the reel of film is passed down to the projection box for inclusion in the programme of the theatre. Photographs and certain technical details of the rapid processing machine are given. The Kodak hot process is used in which film travelling at 90ft. per min. is completely processed for projection in 40 sec. T. M. C. L.