The motion picture projectionist (Nov 1930-Oct 1931)

42 Motion Picture Projectionist March, 1931 More than 1,200 satisfied users of SYNCROFILM are the best guarantee of quality, economy and service ....,_■■ ^' ,.. "_./ ■. ^ rj -■:■ High Points of SYNCROFILM No Friction on Film — -Rolling Contact Throughout No Possible Injury to Film Patented Optical System Delivers Light Beam One-Half Thousandth of One Inch Wide of High Intensity AH Rollers Ball Bearing. All Parts Chromium and Sound Head for Simplex Cadmium Plated. For Simplex, Powers, and Motiograph Projectors WEBER MACHINE CORP. 59 RUTTER ST. ROCHESTER, NEW YORK Export Department Cable Address 15 Laight St., N. Y. C. "ARLAB" New York Hoffmdnn-Soons PERPRCTIDN ^y V LOOK AT YOUR LOSSES Sound screen and color are the hijackers of light rays — taking, with other losses, approximately 80% of your a.npsrages. In hundreds, if not thousands, of theatres, crowded attendance is thinning out. Profits shrinking. Because pictures are projected with insufficient light. Swell your box office receipts with the remedy — Perfection Multiple Coil Rheostats, the world's best. Let us mail our new catalog telling all about it. THE ONLY UNION MADE RHEOSTAT Sold by Sam Kaplan, and National Theatre Supply Co., New York, and by your dealer. HOFFMANN-SOONS Ele ctrieal and Engineering Corporation 387 First Avenue Mfg. Division New York Contracting Electrical Engineers^— Moving Picture Theatre Electrical Specialists from within the set. (3) Of other apparatus, not functioning. DECIBEL. Unit of gain and loss of energy, intensity, loudness. Equal to ten times the logarithm (to the base 10) of the ratio I/I0 where I is final intensity and I0 is initial intensity in a transmitting system, or (when the decibel is used as an' absolute unit) I0 is a standard intensity. Other names and abbreviations are db, SU, sensation unit ; TU, transmission unit. Note : The logarithm ol 2 is 0.3 very nearly, therefore intensity is doubled for each gain of 3 db. DENSITOMETER. Apparatus for measuring densities, as of photographic films. DENSITY. (1) Logarithm (to the base 10) of capacity; capacity is the reciprocal of transmission (set1 transmission). Thus a film transmitting 100% of the light has density 0 ; transmitting 10%, density 1 ; transmission 1%, density 2 ; etc. To add a density of 0.3 is to cut transmission in lialf. (2) Mass of a substance divided by its volume. DENSITY, DIFFUSE. See diffuse density, DENSITY, ENERGY. See energy density. DENSITY, SPECULAR. See specular density. DEPTH OF FIELD. The range of object distances within which objects are in satisfactory sharp focus in a photograph. DEPTH OF FOOTS. (1) Same as depth of field. (2) The range through which a photographic plate can be moved forward and backward with respect to the lens while maintaining satisfactorily sharp focus on an object at a given distance. DEUCE. Piece of lighting equipment for housing 2-kilowatt incandescent lamp. DEVELOPER. Chemical solution having 1 be property of resolving latent photographic images on exposed film into metallic form. DEVELOPMENT. Process of chemically treating an exposed photographic emulsion to make the latent image visible. For details, see first emulsion, then exposure; also see fixing. DIAPHRAGM. Thin plate, generally metal. In a camera, the iris-like device consisting of movable curved blades which may be adjust d to control the limiting aperture. (See aperture, limiting.) In a microphone, the front vibrating plate. i DIELECTRIC. The insulator in a con! denser. DIFFRACTION. Bending of waves around an obstacle. DIFFUSE DENSITY. The value of den. sity obtained when transmission is measured for diffuse light — e.g., light transmitted through the negative in a contact I printer. DIFFUSER. Device of silk or gauze placed over lights to diffuse the rays. For ; exteriors, a frame of similar material to diffuse sunlight. DIMMER. Rheostat to regulate intensity of incandescent lamps. DISC CONDENSER. Kind of condenser, variable. DISCHARGE TUBE. A closed tube (generally glass) from which most of the air and other gas has been pumped out, i and into which a small amount of inert • gas is introduced. This gas is capable of conducting an electric current when volt, age is applied to the tube terminals, and, : in doing so, will emit light more or less in proportion to the amount of current flowing. DISSOLVE. The gradual change of one scene into another, made by lapping the fade-in of the one on the fade-out of the other. If accomplished by double exposure or double printing on the same strip of ; film it is known as a lap-dissolve. DISTORTION, BARREL. See barrel distortion. DISTORTION, PILLOW. See pillow distortion. DOG LEG. Kink in the starting spiral on a disc record, due to an imperfection in the spiral-cutting mechanism. DOLLY. Any small rolling platform. | Sometimes, specifically, one large enough to