The motion picture projectionist (Nov 1930-Oct 1931)

40 Motion Picture Projectionist March, 1931 Good Projection Requires Good Rectification M. P. 25-25 Good Rectification Means Forest Rectifiers THIS Forest Rectifier meets the demand for a single unit to supply direct current for two projectors, and will funish 15 to 25 amperes to either projector continuously. It supplies a steady direct current, free from pulsations, and will produce a better light than other current supply devices. The only wearing parts are the bulbs which will last at least one thousand hours and usually much longer since only two bulbs are being used at a time (except during change over) and the load is alternately carried first by one set of two tubes then the other two as the projectors are alternately used. This Forest Rectifier embodies the use of four rectifier tubes which are connected to supply current to two direct current circuits independent of each other thus preventing loss of current at the first arc when the second arc is struck. Both arcs can be operated at the same time during the change over period and there will be no diminishing of the light from one projector while lighting up the second. Two Ammeters are mounted on the unit which will show at a glance the amperage being used at either arc. Links are provided for operating from 110-220 or 240 volts. Rectifiers for all purposes made in 15 amp., 25-25 amps., 30, and 65 amps. sizes. We are specialists in our field. Send us your technical problems. Literature on request. Forest Electric Corp. New and Wilsey Sts. Newark, N. J. in reproduction, due to irregularities in the sound track. BUNGALOW. Same as blimp. BURNED UP. Over-exposed. BUTTERFLY. Silk cloth on frame used to soften light when making exteriors. See diffuser. BUZZARD. Bad photographic take. B. X. Same as conduit. BY-PASS CONDENSER. Condenser used to separate alternating and direct components of current. "C" BATTERY. . Small battery ordinarily used for supplying negative potential in the grid circuit of a three-element vacuum tube. CABLE. Heavy, well-insulated bundle of wires for conducting electricity. CAM. In general, a non-circular rotating piece in a mechanisim. In particular, the device which operates the intermittent movement of the film in a motion picture camera, printer, or projector. CAMERA ANGLE. Angle of view taken by the motion picture camera. Usually refers to the horizontal angle but occasionally refers to vertical angle. CAMERA BOOTH. Soundproof booth, containing cinematographer and his equipment. The camera is operated in this to prevent noise of camera mechanism from reaching microphone. Camera booths are not now in general use, the camera being placed in a blimp. CAMERA LINES. The boundaries of the region which is in good focus for the camera lens being used. CAMERA MARKER. Marker (q.v.) for the camera. CAMERA MOUNT. Any kind of camera support other than a tripod. CAN. (1) Metal container for film. (2) Ear-phone used for monitoring (cf. monitoring (1).) CANADA BALSAM. Transparent gum used in cementing lenses. CANARIES. Unidentified high-frequency noises in the recording system. CANDLE. Abbreviated form of candlepower (2). CANDLE-POWER. (1) Luminous intensity of a light source, measured in luminous flux emitted per unit solid angle. (2) Unit of candle-power, (1) equal to the luminous intensity of a certain type of standard for BRILLIANT SOUND REPRODUCTION Visitron Photoelectric Cells offer the operator of sound-on-film equipment three decided advantages . . . (1) They practically eliminate "static" noise caused by the amplification of foreign electric currents. (2) They give longer service. (3) Every Visitron cell is guaranteed for six months against defects in materials and workmanship. Throughout their exceptionally long period of dependable service usually well over a year— Visitrons will bring your theatre the clearest, best-defined "sound" that it is possible to obtain with any given type of sound-on-film equipment. Visitron Photoelectric Cells are distnbuted through National Theatre Supply Com. _ _ Pany. Order them from any A'a W H tional Branch or write us direct WL jjf for further information. m LABORATORIES 1803 Grace St. Chicago, 111. candle burning under certain standard conditions. CAPACITANCE. The measure of the quantity of electricity a condenser can hold. It equals the quantity stored divided by the voltage (pressure) storing it. CAPACITY. Same as capacitance. CAPACITY, CARRYING. Current a conductor can carry without becoming overheated. CAT WALK. Narrow overhead bridge. CATHODE. Negative terminal of an electric device (cell or tube), from which the current (in the conventional direction) leaves the device. CENTRE LENS. In a three-lens condenser, the middle one of the three lenses. CENTIMETER. Unit of length in the metric system. Equal to 0.393,7 inch. Abbreviated cm. CHANGE-OVER. In projection, the act of changing from one projector to another (preferably without interrupting the continuity of projection) ; or, the points in the picture at which such a change is made. CHANGING BAG. Light-tight bag, used in changing undeveloped films. CHANNEL. A complete set of recording equipment from 'microphone to film or disc recording units, inclusive. CHARACTERISTIC, CHARACTERISTIC CURVE. Graph showing the essential features of the performance of a photoelectric cell, vacuum tube, photographic emulsion, or other piece of apparatus. For a film, the curve shows how transmission, or density, varies with exposure (see exposure). CHOKE, CHOKE COIL. Coil of wire wound on an iron core and thus possessing high inductance. CHROMATIC. Relating to color. CHROMATIC ABERRATION. The production of color fringes in the image formed when white light is passed through a lens, due to the fact that the lens bends the light rays of different colors by slightly different amounts. CHUTE, DOWN THE! Order to send sound into the amplifier room. CINCHING UP. Tightening a roll of film by holding the center and pulling on the outer end. This is liable to injure the film. CINOPHOT. -Pocket photometer for determining the proper exposure for film. CIRCLE IN. Same as iris in. CIRCLE OP CONFUSION. Round image of a point of light not in focus. The circle of least confusion of a lens is the smallest circle of confusion obtainable with the lens by the best possible adjustment of focus. CIRCLE OUT. Same as iris out. CIRCUIT -BREAKER. Switch which opens a circuit automatically when the circuit becomes overloaded (or else, for some types of breaker, underloaded). CLAW. Type of mechanism for intermittent movement. Cf. in-and-out movement. CLEAN recording channel is one which has practically no unwanted noises in its output. CLICK YOUR HORN! See horn, click your! CLICKS, O. K. ON THE! See O. K. on the clicks ! CLIP. Form of snap fastener for making electrical connections. CLOSE -UP. Picture taken showing Characters or objects at a short distance. Lenses for close-ups have generally a focal length greater than three inches. cm. Abbreviation for centimeter. COCHLEA. Part of the inner ear in which the auditory nerves terminate. COEFFICIENT OF SOUND ABSORPTION. When sound energy strikes any substance, it is partly reflected, partly transmitted, and partly absorbed (converted into heat). The percentage of energy absorbed by a given object is the object's absorption coefficient. COLLECTING LENS. In a three-lens condenser, the lens nearest the light source. COMMUTATOR. That part of a dynamo that changes direction of currents, so that