Showmen's Trade Review (Oct-Dec 1946)

SHOWMEN'S TRADE REVIEW, November 9, 1946 THEATRE DICTIONARY {Continued jrom Page E-¥l) degree of achromatic stimulus. (2) In practice, any extremely dark, dull color. (3) The absence of visual light. Black Body. A perfect radiator and absorber of electromagnetic energy. The properties of incandescent tungsten and carbon approximate those of a black body. Black Light. Radiant energy lying outside the visible range, especially light in the near ultra-violet region of the spectrum which is converted to visible light by the action of suitable fluorescent materials. Blast Heater. A set of heat transfer coils or sections used to heat air which is drawn or forced through it by a fan.' Bleeding (of color). The diffusing of dye away from a dye-image; most noticeable where dark areas adjoin light areas in a picture. Bloop. The sound producd when an imperfect splice in a sound track passes through the sound reproducing mechanism of a motion picture projector. Blooping Ink. Opaque (black) ink used to cover the joint of a sound track splice to prevent the splice from making a noticeable noise when passing through the projector. Blooping Patch. Triangular or oval black section introduced over a splice in the positive sound track, to prevent the noise which the splice would otherwise cause during reproduction. The patch effects a relatively gradual diminution in the transmitted light, followed by gradual restoration to the original value. The sound frequency due to a properly blooped patch is too low to be heard.' Blue. The preferred name for the color of the threecolor additive primary which consists of light in the range 400-500 millimicrons. Boiler Heating Surface. That portion of the surface of the heat-transfer apparatus in contact with the fluid being heated on one side and the gas or refractory being cooled on the other, in which the fluid being heated forms part of the circulating system ; this surface shall be measured on the side receiving heat. This includes the boiler, water walls, water screens, and water floor.' Boiler Horsepower. The equivalent evaporation of 34.5 lb. of water per hour from and at 212 F. This is equal to a heat output of 970.3 x 34.5 =: 33,475 BTU per hour.' Bordering. A manipulation resulting in creating the "stereoscopic window" through which a three-dimensional picture seems to be seen. Box Light. A lamp, consisting of a cluster of incandescents mounted on a pedestal stand. Unlike the btinchlight, it does not include a reflector. Breezing. Said to occur when projected picture is blurred as a result of distortion of focus in camera, printer, or projector — due to uneven shrinkage of negative or positive, or to perforations of uneven pitch.' Bridging Amplifier. Any amplifier or relatively high input impedance, so that a number of such units may be connected in multiple across a relatively low impedance circuit without materially affecting its electrical condition and without reaction on one another. Abbreviated B.A.' Brightness. (1) A photometric measure of light emission per unit area of a luminous body or of a translucent or reflecting surface, i.e., candle-power per unit area. Brightness determines the stimulus value of a given surface as a visual object, and this sense is conveniently expressed in candSfcs per square meter or in millilamberts. B — = dI/(dA cos <r) Brightness is the luminous intensity, I of a surface (real or virtual) in a given direction, rr, per unit projected area of the surface. A cos tt. Note: In practice ao surface follows exactly the cosine formula of emission or reflection ; hence the brightness of a surface generally is not uniform but various with the angle at which it is viewed. Some common units of brightness and their relations are ase follows : 1 candle per square inch = 452 foot-lamberts = 0.487 lambert = 487 millialamberts 1 foot-lambert = 1 lumen per square foot = 0.00221 candle per square inch = 1.076 millilamberts 1 lambert = 1 lumen per square centimeter = 1000 millilamberts = 929 foot-lamberts = 2.054 candles per square inch 1 millilambert = 0.929 foot-lambert = 0.002054 candle per square inch The candle per square inch and lambert are commonly used for high brightness such as light sources. The foot-lambert and millilambert are used for ordinary illuminated surfaces, The foot-lambert equals incident toot-candles times reflection factor, assuming a diffusing surface or medium. (2) Degree of resemblance to white. In common usage the term brightness often refers to the intensity of sensation which results from viewing surfaces or spaces from which light comes to the eye. Brilliance. The characteristisc of a color whidi determines the intensity of the sensation it produces in the eye of an observer. British Thermal Unit. A unit of energy defined in terms of the international steam-table calorie through the convenient relation 1 BTU per pound per degree Fahrenreit = 1 cal per gram per degree Centigrade. It is approximately the quantity of heat required to raise the temperature of 1 lb. of liquid water from 63 to 64 F.> Brush. A device for making electrical contact between the rotating commutator of a generator and the stationary circuit wires. Brushes are made from carbon, copper wires, copper strips and copper gauze, but carbon brushes are most largely used. Brush Loss. Loss, in watts, due to lack of perfect electrical contact between brush and commutator. May be greatly increased by dirty brushes, dirty rough commutator, or lack of sufficient pressure between brushes and commutator. BTU. See British Thermal Unit. Buckle. Unflatness of a motion picture film due to the edges shrinking while the film was in the roll. Bunchlight. A floodlight containing up to ten or more incandescent lamps, mounted on a pedestal stand. B.X. A flexible metal tubing for the protection of electric wires, much used for interior work. A flexible metal conduit. By-pass. A pipe or duct, usually controlled by valve or damper, for conveying a fluid around a main control valvs or damper.' c "C" Power Supply. Device for supplying current to apply a grid bias ; connected between the cathode and grid of a vacuum tube. Calorie. (Large calorie or I.T. kilocalorie) is equal to 1000 international steam-table calories = 1/860 international kilowatt hour. For practical purposes it may be considered as 1/100 of the heat required to raise the temperature of 1 kilogram of water from 0 to 100 C Cam. In general, a non-circular rotating piece in a mechanism. In particular, the device which operates the intermittent movement of the film in a motion picture camera, printer, or projector.' Camera Angle. The angle of view taken by a motion picture camera in photographing a scene, usually referring to the angle in a horizontal plane but it may be used as the angle in any plane. Candle. The unit of luminous intensity. In the United States a specified fraction of the average horizontal candlepower of a group of 45 carbon-filament lamps preserved at the National Bureau of Standards.' Candlepovrer. Luminous intensity expressed in candles.' Capacitance. The measure of the quantity of electricity a condenser can hold. It equals the quantity stored divided by the voltage (pressure) storing it.' Capacitative Coupling. Coupling of one circuit with another by means of a capacity common to both. Capacity, Carrying. Current a conductor can carry without becoming overheated.' Carbons. The carbon rods or pencils used in an arc lamp. Carbon Jaw. The jaw of an arc lamp by means of which carbons are gripped and held in place. Carrying Capacity. The greatest number of amperes an electrical conductor can safely carry. CaEed Class. Glass composed of two or more layers of different glasses, usually a clear, transparent layer to which is added a layer of opal, opalescent or colored glass.' Cel Side, Celluloid Side. On a motion picture film which carries an emulsion on one side only, the side on which the base is exposed or which is opposite to she "emulsion side." Central Fan System. A mechanical indirect system of heating, ventilating, or air conditioning, in which the air is treated or handled by equipment located outside the rooms served usually at a central location, and is conveyed to and from the rooms by means of a fan and a system of distributing ducts.' 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. 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 bow transmission, or density, varies with exposure. Chimney Effect. The tendency in a duct or other vertical air passage for air to rise when heated, owing to its decrease in density.' Choke, Choke Coil. Coil of wire wound on an iron core and thus possessing high inductance.' Chromatic Aberration. The failure of a lens or opti cal system to unit into a common focus the rays oi light of different wavelengths eminating from a pointobject. The variation in image position with wavelength may be in respect to (1) distance from the lens to the image in the direction of the opLical axis (longitudinal chromatic aberration), or (2) distance from the optical axis to the image in a direction at right angles to the axis (radial chromatic aberration). Cinch Marks. Short scratches on the surface of a motion pitcnre film, running parallel to its length, and caused by improper winding of the ixill which permitted one coil of film to slide on another. Cine. A prefix used to refer to the motion picture irt, or motton picture apparatus; probably originating as an abbreviation for cinema or cinematograph. Circle of 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 I he lens by the b«st po.ssible adjustment of focus. Circuit Breaker. .\ device, somewhat similar to a switch, by means of which a dangerous variation in current flow will operate electro magnets and open the circuit. Circuit breakers are made to operate Ixjth for over-and-under-load. Class A Amplifier. Amplifier whose grid bias and alternating grid voltages produce a plate current thai flows at all times in a specific tube. Class AB Amplifier. Amplifier whose grid bias and alternating grid voltages produce a plate current that flows less than the full, but more than half the electrical cycle. Class B Amplifier. Amplifier in which the plate cuj rent in a specific tube flows for about one-half of each cycle with grid voltage applied but in which plate current is zero without grid voltage applied. Class C Amplifier. Amplifier in which plate corrent in each tube is zero when alternating gnd voltage if not applied. Coefficient of Heat Transmission. The amoimt of heat (BTU) transmitted from air to air in one how per square foot of the wall, floor, roof or ceiling for s difference in temperature of 1 F between the air or the inside and that on the outside of the wall, floor, roof or ceiling.' Coefficient of Sound Absorption. When soand enerffj strikes any substance, it is partly reflected, partlj 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.' CoUimated. A beam of light is said to be collimated when all of its rays have been made paralld. See Si>ecular. Color Analyzer. (I) A colorimeter. (2) An instrument used to determine the relative brightness of light of different wavelengths reflected or transmitted by a substance or emitted by a source. Color Blindness. Any of various types of abnormal vision which impair the ability of the abnormal eye to detect color differences and relationships which an apparent to persons having normal sight. In total oolcw blindness, all colors appear as greys; the more usual partial color blindness (dichromatism) is marked by the inability to distinguish between certain pairs, tor ex ample : red and green. Color Box. A device holding gelatines of different colore and permitting one to be substituted for isother or two or more to be used together. Color Frames. Devices in which gelatine sheets arr mounted. Color Match. Two samples of light or colored materials are said to be a visual color match if they produce identical color sensations when viewed under somf stated condition. Two samples of light or colored materials are said to be a physical color match if they produce identical color sensations when viewed under all possible conditions. Color Mixture Curves. See Color Sensation Curves Color Photography. Any process in which an attempt is made to reproduce the light-and-shade and color of a scene by photographic means. Color Sensation Curves, Excitation Curvas. Curves based upon the response of the normal human eye, showing the relative excitations of the three elementary . sensations, according to the Young-Helmholtz theory of color vision. Color Sensitivity (Photographic). The sensitivity of a photographic material to light of various wavelengths : The color sensitivity may be measured by making a wedge spectrogram using the particular light souroe. emulsion, and developer that are being studied. Color Temperature (of a Light Source). The tem perature at which a black body radiator will visuallj match the color of the source. Color temperatures art commonly expressed on the absolute scale in degree? Kelvin. Color Wheel. A device capable of being rotated, for holding gelatines and for permitting one to bf ■substituted for another as required. May be motor driven. Coma. An unsymmetrical spherical aberration of a lens in a principal plane of an oblique pencil of light In the presence of coma, a point-object off the axli of a lens is imaged as figure resembling the genera' appearance of a comet, the tail of which may b» directed toward the optical axis or away from it. Comfort Air Conditioning. The process by whicli simultaneously the temperature, moisture content, movement and quality of the air in enclosed spaces intended for human occupancy may be maintained within required limits.' Comfort Line. The effective temperature at which the largest percentage of adults feels comfortable.' Comfort Zone (Average). The range of effectivf temperatures over which the majority (50 per cent oi more) of adults feel comfortable. Comfort Zone (Ex treme) : The range of effective temperatures ovei which one or more adults feel comfortable.' Commutator. That part of a dynamo that changes ilireclion of currents, so that the current flowing in the outside circuit will remain d.c' Commutator Ripple. Small alternations in the emi produced by a d c generator, due to the operation of the commutator. This ripple is the chief cause of arc hum.' Complementary Colors. Two colors are said to bf complementary when their spectral properties are related in any of the following ways: (1) Additive Complementary Colors: Two colors are complemeiitary if they can be combined additively to form a visual neutral. For example, the colors might be blue and yellow papers whiah can be combined as sectors Or a spinning top to produce a visual grey. (2) Siibtractive