International projectionist (Jan-Dec 1940)

jtf* MAGNESIUM COPPER SULPHIDE RECTIFIERS You owe it to yourself! BECAUSE ... They are modern, dependable and economical. BECAUSE . . They are the only rectifiers using tested P. R. Mallory Magnesium Copper Sulphide rectifying units, whose immunity to projection room heat factors has been proved. BECAUSE ... They meet successfully and efficiently the amperage requirements of today — even when two lamps or a spotlight must be operated from ONE Rectifier. BECAUSE ... The simplicity of construction found onjy in Magnesium-Copper Sulphide Units is vaur VISIBLE guarantee against neer'less multiplicity and complications. BECAUSE ... The reliable 3phase fail — magnetic switches — protective fuses — sturdy and scientifically designed outer ONE PIECE case — all are exclusive Forest features. BECAUSE ... They solve, with ease, all the problems encountered in present-day projection power supply. BECAUSE . . . They are DESIGNED and ENGINEERED exclusively FOR THE PURPOSE FOR WHICH THEY ARE INTENDED. Write for Information the circuit, and the less the filtering delay, the smaller can the margins be made without causing too frequent clipping. A number of circuits are discussed which have been proposed for improving the filtering without sacrifice of quick opening, or reasonably rapid closing. In some operations, anticipation is entirely practical, and if this is done it appears possible to provide an almost perfect envelope current. EDITING A MOTION PICTURE I. J. Wilkinson and W. Hamilton RKO Radio Pictures, Inc. The paper is an attempt to reduce to words a portion of the mechanical and artistic elements involved in the process of editing a motion picture. The authors realize that they are dealing with a highly controversial subject but feel that, as there is so little pertinent material "available on the phase of motion picture production, this paper may serve as a preliminary to a study on a larger scale. Consideration is given to the origin of film editing and its advancement from the purely mechanical craft of the early days to its present status as a contributing factor in the entertainment and dramatic values of the motion picture of today. Demonstration film is presented to illustrate various editing technics and to show the possibility of their use as a means of drastically altering original story and dramatic conception. A METHOD OF CALIBRATING MICROPHONES F. L. Hopper Electrical Research Products, Inc. and F. F. Romanow Bell Telephone Laboratories Methods of determining the performance characteristics of microphones by acoustic measurements are described. Factors involving the accuracy of the methods are discussed. The correlation between a microphone's performance as determined by acoustic measurement and by listening tests is reported. Application of both types of test to a studio type of cardioid microphone are given as an example. LINE MICROPHONES H. F. Olson RCA Manufacturing Co. A line microphone is a microphone con sisting of a large number of small tubes with the open ends, as pick-up points, equally spaced along a line and the other ends connected by means of a common junction to a transducer element for converting the sound vibrations which converge upon the junction into the corresponding electrical variations. Several types of line microphones with the useful directivity along the line axis are described as follows: a simple line, STOP/ MUTILATING FILM WITH SCRATCHES . . CRAYON BLOTCHES . . PUNCH HOLES SIGNO-MARKER places change-over signal marks and outlines hard-to-see marks easily, neatly and accurately on one to four frames in Standard dot position. If your dealer can't supply you, order direct on 10 Day Trial Money-Back Guarantee. Only $Z.50 postpaid. WRITE FOR CIRCULAR CLINT PHARE PRODUCTS 282 E. 214 St. EUCLID, OHIO with KNOWLEDGE Helping thousands of frightened people to regain their peace of mind ...this is one of the most constructive services of the New York City Cancer Committee of the American Society for the Control of Cancer. Your peace of mind will be helped by your support of the Committee's work through the purchase of its labels. Mail your dollar today. You will receive a book of package labels and the Quarterly Review, and you will share in a vital service. ■ mtm ■• mm mm m* ne ■■ mm ^m mm mm mm tmm m New York City Cancer Committee of the American Society for the Control of Cancer 130 East 66th St., New York, N.Y. For my $1.00 please send a supply of package labels and the Quarterly Review. street state city If you live outside the Metropolitan area, write to — American Society for the Control of Cancer, 350 Madison Avenue, New York, N.Y. 28 INTERNATIONAL PROJECTIONIST