The motion picture projectionist (Nov 1929-Oct 1930)

30 The Motion Picture Projectionist January, 1930 neutralized the static charge, some of the dust was released and settled on the bottom. But in present day practice the dust on film has no such chance to escape from the surface but instead becomes embedded and permanently locked in the surface by the binding clampage of the layers on the reel. Figures 2 and 3 show what happens to the cinegraphc and phonographic tracks and surfaces of the film through the operation of the static electricity and dust combination. Fig. 2 shows a section through two layers of film as they are contained in the reel. A represents a section through the emulsion of a fresh film, while B represents the celluloid portion. The small dots through the layer A represent the halids of silver which form the image of a picture or the shaded parts of a sound track. This is known to the projectionist as "grain" and are plainly visible as such on the screen during projection. This represents a film in prime condition. Fig. 3 represents a section through two layers of used film, with the black "arrowheads" or "cobblestones" representing grains of dust or grit which have been embedded in the emulsion, -A-; the upper edges of these are seen to be projecting into the celluloid surface of the next layer -B-. It will be noted how both these surfaces are distorted by strain on account of the embedded grit. It may be seen how both the celluloid and emulsion surfaces are gashed and furrowed by the grit plowing through them when one layer is pressed taut upon another. Some of the "stones," it will be noticed, cut entirely through the emulsion, and, of course, the image in the track of these is cut away altogether and only a light streak remains. These furrows afterward become filled with fine dust, and this is the "black rain" so familiar to both audience and projectionist. It is quite evident that any process of renovation can only remove the dust accumulated in these furrows and cannot replace the missing sound and picture portions; nor will such a process remove the grit embedded in the surfaces, which must necessarily be left there to produce new furrows, due to slippage and cinchage in subsequent take-up and rewind actions. (To be continued) Standard Nomenclature ii (The following glossary of technical terms used in the motion picture industry was formulated by an S. M. P. E. committee and adopted as standard by that organization. Trans. Vol. XIII, No. 37.) M MICROPHONE — A device for conversion of sound into electrical pulsations. Microphone Amplifier — The first unit in the amplification chain, usually placed close to the microphone. Microphone Mixer — -An assembly of volume controls used for regulating the relative input signals from several microphones. Milli-Prefix signifying the thousandth part of, as in millimeter, millivolt, etc. Modulation (Electrical) — The variation of amplitude of an alternating current in accordance with the amplitude of a second alternating current or complex wave. As used in sound recording practice, the superposition of an alternating current on a direct current. Monitor — (verb) — To control the volume of sound from a reproducing equipment. Monitoring Loudspeaker — A loudspeaker located in the recording room and connected with the microphones on the set to permit the recordists to hear the sound being recorded. A similar speaker is placed in the projection room to enable the projectionist to follow the sound reproduction. Motion Picture — The representation of an object by the rapid presentation to the eye of a series of pictures showing the object at successive intervals of time. Motion Picture Projector — A device for suitably projecting motion pictures. Moving Period — That portion of the picture cycle during which the film at the aperture is in motion. This period is expressed in degrees of revolution of the flywheel when 360 degrees are equal to one cycle. Multiple Reel Picture; — (As applied to 35 mm. film) — A photoplay of too great footage to be placed on a single 1,000-foot reel. In practice a term applied to photoplays requiring more than three 1,000-foot reels to hold it; photoplays of two and threereel length being termed "two-reelers" and "three-reelers." N Negative — The developed film, after being exposed in a camera. Negative Stock — Light-sensitive film intended for motion picture camera use. o Objective — The simple or compound lens nearest an object which forms an image of it. Observation Port — An opening in the wall of a projection room through which a projectionist observes the screen. Ohm — A unit of resistance, reactance and impedance in a conductor to the passage of an electric current. Optical Axis — The straight line through the centers of the light source, lenses, diaphragm, etc., of an optical system, to which their planes are in general perpendicular. Optical Scratch — Any particle of dust or mechanical imperfection in the slit will be imaged on the sound track and have much the same effect as a scratch on the sound track parallel to the edge of the film. This is called an optical or shadow scratch. Optical Wedge— A device which varies progressively in absorption of light from end to end. Sometimes used as a device for varying exposure in sensitometry. Orthochromatic Emulsion — One which is made sensitive to yellow and green as well as blue and violet. Orthochromatic Photography — Photography in which colored objects are rendered in monotone according to their true visual brightness. Oscillograph — A device for recording vibrations of high frequency. P Panchromatic — -Referring to emulsions which are made sensitive to the entire visible spectrum. Phase — In uniform circular motion, simple harmonic motion, or in the periodic changes of any magnitude varying according to a simple harmonic law (as sound vibrations, alternating current changes, etc.), the point or stage in the period to which the rotation, oscillation, or variation has advanced, considered in its relation to a standard position or assumed instant of starting. Phot — A metric unit of illumination. It equals one lumes per square centimeter. Photo Electric Cell — A cell consisting of a sensitive surface as the negative electrode and a positive electrode between which electrons will flow when the sensitive surface is illuminated. Photo Electric Effect — The emission of electrons resulting from the action of light. Photo Electric Sensitive Surface — A surface which emits electrons under the influence of radiation of certain frequencies. The threshold or minimum value of the frequency necessary to produce photo electrons depends on the composition and the nature of the surface. Photometry — The measurement of light. Photoplay — A story in motion pictures. Photo Sensitive Surface — Any surface that responds to radiation. Picture Cycle — The entire series of mechanical operations which takes place between the positioning of one frame of a motion picture film and the positioning of the next frame. Positive — The developed film, after being printed from a negative. Projectionist — A person skilled in (Continued on page 41)