Motion Picture News (Oct-Dec 1930)

October 4 , 1 930 M o I i n n P i el it r e X e 7c .f 93 Manager's Self Quiz (Reprinted from Publix Opinion) Theatre Illumination Q. When choosing a dimmer, how shall one determine its capacity/ Whyt A. Choose a dimmer having the same rated capacity as the load it is going to control. When the dimmer capacity is higher than the load, the light will not be dimmed out entirely and changes of brightness will be sudden instead of gradual. If the dimmer is of lower capacity than the load it is compelled to carry, the cut-out will occur too rapidly and the dimmer will be burned out in time. Q. How can one determine the size of letters on inside illuminated signs? A. The formula for determining the size of letters on a sign is as follows. The greatest viewing distance in feet divided by thirtysix will give the height of the letter in inches. For a viewing distance of 72 feet for instance, a height of two inches for the letters would be necessary. Width of a letter should be 60 per cent of the height while space between letters should be 40 per cent of the height. Q. In illuminating statuary what must be borne in mind? A. All statues when illuminated cast shadows. It is important to get the statuary looking as natural as possible. For that reason, illumination should come from two sources so placed that a natural result will be obtained. Q. Should high wattage lamps be dipped? Why? A. It is impracticable to dip lamps of SO or higher wattage because such lamps are generally gas filled and the dip would burn off rapidly. Q. What is the depreciation in the efficiency of lighting equipment due to dirt? A. On the average there is a 20 per cent loss in the efficiency of light equipment in a month because of the accumulation of dust and dirt on lamps and reflector surfaces. Q. What is the best system of cleaning to prevent this depreciation? A. Wash and clean all lamps once every three months. Have them wiped with a damp cloth once every month. Dry wiping is not very effective and costs almost as much as damp wiping. Do not use it. Projection Q. What are the most common carbon defects in projection? A. Burned out craters caused by too low amperage ; blown out core caused by two high amperage; excessive spinkling caused by too much current, or by poor contact between carbon and holders ; sputtering at the arc caused by damp carbons, improper set or trim of carbons. Q. How do these faults spoil projection? A. Burned out craters result in dark spot on the screen ; blown out core results in increased carbon consumption, spot on the screen and spindling ; excessive spindling results in flickering light on the screen: sputtering at the arc results in flickering light on the screen. Q. What remedial steps would result in improvements:' A. Remedv for burned out crater — use a smaller carbon or increase the current. Remedy for blown out core — use less power or use carbon of greater diameter. Remedy tor excessive spindling — use proper carbon for specified current and make sure that contacts are smooth. Q. How should a carbon be tested for breakage? A. Remedy for sputtering at the arc— dry carbons by placing on top of rheostat. Check up on set and trim. Copper coated carbons may be broken under coating. Test not by tapping carbon on hard surface but by applying slight pressure with the fingers along entire length of stick. Tapping a carbon spoils it. Q. What projection defects occur most commonly? A. Common projection defects are unsteady pictures, poor definition, travel ghost, flicker, distortion, poor illumination, blank screen, improper projection speed resulting in unnatural movement of subject, fuzzy border, and misframes. Q. What are the causes of an unsteady picture, poor definition, and flicker? A. An unsteady picture is caused by (a) excessive speed of projection, (b) bent intermittent sprocket, (c) insufficient tension on shoes (d) wax or dirt on intermittent sprocket, (e) film perforation not standard, (f) film shrinkage, (g) improper splicing. Poor definition is caused by (a) dirty objective lens, (b) incorrect lens system, (c) reflected light from lens barrel, (d) warped film, (el soft focus film or duplicate film, (f) vibration of projector, (g) haze from wrong type of screen, (h) uneven track on shoe and plate. Flicker is caused by (a) projection speed too low, (b) light source too strong, (c) unsteady arc, (d) douser not properly timed for change over, (e) iris not properly timed. Q. What steps would you take to increase illumination on the screen? A. Clean dirty condensers, check to see if insufficient current, check on correctness of optical system, avoid using dense film, make sure that image of light source does not appear on screen. Q. What three types of film damage are prevalent? A. Damage to sprocket holes, scratches on the body of the film, and deliberate mutilation of the film for signal purposes. 0. What are ten causes of sprocket damage? A. Improper adjustment of the tension Coloring Exteriors CHICAGO— outlining of buildings in color lights is being developed by a number of theatre operators. Reco color hoods with holders are particularly suitable for this work, states Reynolds Electric Co., manufacturer and distributor. Reco hoods are used in providing color in auditoriums, for exit lights. borders and footlights. Natural colored glass is used. ^toes, poorly made splices, damaged film reels, badly notched sprocket holes, the use of old and brittle film, overspeeding, projector parts badly worn, defective mechanism of projector, improper lubrication, and worn or undercut sprocket teeth, dirt on intermittent sprocket causing film in extreme cases to ride on teeth. Sound Q. What procedure must be followed when the reproducer needle jumps a groove on the disc ? A. If the needle jumps back the sound will repeat, and may keep on repeating at every turn of the record. If the needle jumps forward the sound will be ahead of the picture. The procedure will depend on the character of the film and the place where the jump occurs. Any record on which the needle has jumped must never be used again, and the reproducer should be checked as soon as possible. Bring the fader to zero as soon as the jump is noticed. The next procedure will depend on circumstances, as follows : (a) With speech or other sound accompaniment, where exact synchronism is essential. In this case it is not possible to continue without losing synchronism, and there is no option except to continue the programme with the next reel, which is set up on the other machine, or else to cut out the sound for the remainder of the reel. (b) With music or other sound accompaniment, where exact synchronism is not essential. Keep the projector running and look over the reproducer quickly to see whether there is any visible cause for a jump, such as the reproducer body's dragging on record, or the reproducer's hitting something that prevents it from moving freely. If so, remove the obstacle or change the reproducer. This, of course, involves loss of accompaniment for the remainder of the reel. (c) If no cause of the trouble is evident, but the needle jumps back, change the needle, move the reproducer over to a position two or three grooves ahead of where it was when it jumped, and restore the fader to its regular setting. If the needle jumps forward and seems to be 'racking properly, restore the fader to its regular setting. Synchronism is lost when a record is continued after the needle has jumped. In such cases, if there are any direct cues in the picture, such as knocks, voices, cheers, etc., the fader must be put down to zero when passing over them. Q. When do vacuum tubes require replace ment ? A. Vacuum tubes require replacement when any one of the three following conditions occur : (a) When plate currents begin to fall below minimum values. This, of course, applies only >n cases where a meter is provided on the amplifier for the purpose of checking such currents. When two or more amplifier tubes begin to show low plate current at the same time the fault probably does not lie in them but may be due to the rectifier tubes. Therefore try renewing the latter. (b) When the tube begins to be noisy. This statement applies to amplifier tubes. (c) When the filament shows one or more bright spots instead of glowing uniformly throughout its length. Tubes that have once been used in a rectifier are unfit for use in amplifiers since they are not capable of giving good quality.