British Kinematography (1948)

24 TECHNICAL ABSTRACTS Certain of the following abstracts are reprinted by courtesy of Messrs. Kodak Ltd. Most of the periodicals here abstracted may be seen in the Society's Library THE MECHANISM OF PHOTOGRAPHIC DEVELOPMENT : A REVIEW OF THE WORK OF T. H. JAMES. PART I. R. B. Collins, Phot. J., 87b, January-February, 1947, p. 2. The work of T. H. James on the reduction of (a) silver ions, (b) insoluble metal salts, has been reviewed. The evidence supports the view that normal photographic development is a silver catalysed reaction occurring at the silver-silver halide interface. The importance of an ionic protective layer of adsorbed ions is also stressed Author's Abstract. DETERMINATION OF ELON AND HYDROQUINONE IN DEVELOPER. AN EXAMINATION OF STOTT'S METHOD. G. I. P. Levenson, Phot. J., 87b. January-February, 1947, p. 18-24. (Kodak Communication No. 1116H.) The method for the determination of Elon and hydroquinone published by Stott has been found to give low results. The method has been examined in detail and the causes of a number of errors have been located. Methods of eliminating some of these and of compensating for others are described. Details of the experimental technique, including the selection of a suitable indicator, etc., are discussed. Summarised schedules of operations for carrying out the determination of hydroquinone and Elon in a developer containing both, and Elon in a developer containing only Elon, are appended. Using the modified technique the concentrations of Elon and hydroquinone may be determined to within two per cent, of their true value. AN ANALYSIS OF LOW-REFLECTION COATINGS AS APPLIED TO GLASS. W. P. Strickland, /. Soc. Mot. Pic. Eng., July, 1947, p. 27. The author summarises the advantages and principles of anti-reflection coatings and the reason for the colour. He describes a technique whereby a colourless coating can be obtained by means of a continuously variable refractive index. He concludes that the magnesium fluoride coating is the most satisfactory and shows that this protects the glass from chemical abuse. He describes a new method of removing the coating if necessary. M.V. H." A COMBINATION SCORING, RE-RECORDIXG AND PREVIEW STUDIO. D. J. Bloomberg, W. 0. Watson and M. Rettinger, /. Soc. Mot. Pic. Eng., July, 1947, p. 3. The various considerations affecting the acoustic design, recording equipment and detail layout of the new Republic scoring studio are discussed and a description of the scoring and rerecording facilities is given with photographs of the installations. X. L. A NEWLY DEVELOPED LIGHT MODULATOR FOR SOUND RECORDING. G. L. Dimmick, /. Soc. Mot. Pic. Eng., July, 1947, p. 48. The new RCA mirror galvanometer is interchangeable with and follows the same general design as those at present in use. Performance figures for the improved frequency response and freedom from harmonic content and bias effects, are given. The improved performance and stability has been achieved at the expense of a reduction in sensitivity which is well within the capacity of amplifiers now being introduced. N. L. SOUND ABSORPTION AND IMPEDANCE OF ACOUSTICAL MATERIALS. Hale J. Sabine, /. Soc. Mot. Pic. Eng., Sept., 1947, p. 262. The paper reviews the relationship between acoustic-impedance and sound absorption and notes the influence of the physical properties of a medium on these factors. The application of these concepts to practical cases is then dealt with, including the behaviour of both solid backed and air spaced panels. N. L. .