Reel and Slide (Mar-Dec 1918)

plllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllilllllli^ Any questions pertaining to the projection of films and slides | on the screen will be answered by this department. Address i "Projection," Reel and Slide, 418 So. Market St., Chicago. | If an answer by mail is desired, enclose stamped envelope, m iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii^^ Projection All About the Projectors (Many requests reach this office for information concerning the various types of moving picture projectors. Reel and Slide will print in this department a complete description of each machine now on the market for the benefit of its readers. Next month the Pathescope will be described. — Editor.) To project motion pictures, many times more light is required than for lantern slides. With the common condensing lens system enormous loss of light occurs, because the same condensation of light is made to serve for both apertures. The standard motion-picture aperture measures 11/16 by 15/16 inches — the standard slide aperture measures 23^ by 3 inches. Anyone without knowledge of the optics of projection can see that the same illuminating system cannot efficiently and economically cover two areas of • so great a variation in size. The Victor Animatograph employs a double convertible lens system, which is automatically adjusted for the small and large aperture. One position of the lenses concentrates all the light obtainable from the lamp on the small or motion-picture aperture — a simple swing of the lamp house readjusts the condensing lenses to broaden the beam of light to cover the full standard lantern slide aperture. This Victor feature allows great reduction of light in the lamp to produce the same illumination of image on the screen. Reduction of the required light-power of the lamp makes possible the use of incandescent electric globes, with maintained light efficiency. * * * The importance of this Victor feature is threefold: First, comparatively low amount of light is required in the lamp to produce standard brilliancy of illumination on the screen; second, the short focus condensers permit the elimination of all lamp adjustments — the light at its fixed point clearly and evenly illuminates the whole field without adjustment; third, the new high-power incandescent lamp can be used to advantage with the Victor system. Elimination of not less than twelve lamp adjustments common to all lights of equal power — great reduction in heat — great reduction in operating expense — complete elimination of noise. Many variations of lamps are furnished for currents of all voltage — 6 and 8 volt lamps for battery attachment, 28 to 60 volt lamps for use with independent lighting plants, 110 to 125 volt lamps for direct attachment to city lighting circuits. For 220-volt circuits the 110-volt lamp is supplied with a special current-reducing device. AH Victor lamps are interchangeable, the type and size of bulb and base being the same for all voltage variations. The intermittent movement in the Animatograph is an advanced form of the "Geneva" type, or star and cam mechanism. The shaft is carried in one long bearing of phosphor bronze, giving minimum wear, but allowing easy means for adjustment. The movement operates in an enclosed oil case. The wearing parts are made of specially hardened steel, accurately machined to a maximum variation of 1/5000 inch. One of the most important features of the Victor intermittent movement is the speed with which it works. It moves in one-seventh, and is stationary six-sevenths of the interval allowed for the movement and exposure to the light of each individual picture. This means an increased exposure of light period and a decreased dark period, resulting in greater illumination of the image on a given amount of original^ light from the lamp, as well as eliminating flicker. The usual intermittent speed of other machines is four to one. * * * Another feature is that the Victor movement does not tear or otherwise damage the film. Eight teeth of the sprocket wheel actuated by this intermittent movement engage in the perforations on the sides of the film. Because this sprocket starts slowly, moves quickly, and stops slowly, abrupt jerking of the film, which causes tearing the perforations, is eliminated. In the Animatograph there are two two-bladed .shutters, each revolving in an opposite direction. Just before the film is to be moved, one blade of the shutter enters at the top of the aperture, moving downward, another blade enters at the bottom of the aperture, moving upward. At exactly the instant that these two film blades meet in the center of the aperture to cut off the light, the film starts to move. As the shutter blades pass each other, in covering the aperture, the film is in movement. The aperture is again open at exactly the moment that the film comes to rest. One of the most important features of the Victor double two-blade shutter system is that flicker is completely eliminated. The framer lever on the Animatograph is conveniently located on the top of the head, readily accessible from either side or back of the machine. With the Animatograph running at an> speed, the framer instantaneously raises or lowers the intermittent sprocket, and synchronizes the shutter in one operation. The shutter is synchronized with the mechanism so that it "cuts in" at the aperture at exactly the right moment to hide the film travel, no matter what may b«> the position of the intermittent sprocket. A safety shutter is essential because the light at the aperture plate must be shut off when the , mechanism stops; otherwise the heat of the concentrated light will damage the film. The Victor Positive Acting Safety Shutter drops of its own weight to close the aperture when the speed of the mechanism is below normal. * * * The development of the three sizes of Mazda C lamps for the projection of motion pictures has brought out the importance of the auxiliary equipment which must be used with these lamps in order that they may be applied to existing machines. The lamps alone have been advertised by the various lamp manufacturers, but very little information has been given regarding the methods and equipment for applying these lamps so that the best results can be obtained. The question which naturally arises in the mind of the prospective user of the projection lamps is how his apparatus can be changed so as to enable him to replace his arc with the Mazda lamp. On the machine itself the greatest changes which must be made are confined to the lamphouse. The lamp-house equipment for Mazda lamps should provide for the accurate focusing of the lamp and the quick replacement of a lamp which fails while a film is being shown. It is true that under normal conditions the failure of a lamp during the projection of a picture is _ an exceptional occurrence; however, the possibility of such a failure exists and it i? therefore necessary to provide some method of quickly substituting a new source of light. In practically all lamp-house equipments which have thus far been developed there is provision for the adjustment of two or more lamps and in case of the failure of_ one it is necessary only to shift the spare lamp into position and proceed with the picture. The operation of changing the lamps is very simple and can be performed in a few seconds, so that the time that the light is cut off is not much greater than the time consumed in restriking an arc which may have become extinguished. « « « The simplest form of lamp holder consists of a socket fitted with a clamp which is held in the lower carbon holder of the arc lamp mechanism. By having interchangeable sockets or merely by 28 unscrewing the lamp it would be possible to remove one lamp and substitute another in case of a burnout. The second lamp may not be ver> accurately focused because of differences in the mounting height and filament arrangement, but the change could be made in an emergency and the lamp accurately focused before starting the next film. The socket which fits into the lower carbon holder may also have a holder which carries a spherical mirror which is adjusted to throw an image of the lamp filament back upon itself. The effect of the mirror is to improve the light source and therefore give a smoother screen. The mirror not only gives a light source of greater uniformity by filling up the spaces between the coils with the reflections from the mirror, but also returns to the condensing system a considerable portion of the light which would otherwise be wasted. The effect obtained by the use of a mirror is very similar to what would be obtained from a smooth plate of tungsten heated to the temperature of a filament. The Nicholas Power Co., 90 Gold Street, New York, was the first of the standard motion picture machine manufacturers to develop a lamphouse for the use of the Mazda lamp. It is designed to fit any of the standard Powers cameragraphs and is large enough to accommodate either the 600 watt or the 750 watt Mazda lamp. There is not sufficient clearance in this lamp-house for the 1,200 watt lamp. Two condenser systems are provided — one condenser for motion picture projection is a Corning lens which delivers a very uniform spot of light at the aperture plate and therefore results in a screen which is evenly illuminated. In order that slides may be shown the lamphouse carries a pair of plano-convex condensers which may be swung into place when the lamphouse is moved over for slide projection. There are positions for two lamps in the lamp-house. Both lamps may be focused at the convenience of the operator before the show, and in case it is necessary to change a lamp while a picture is being run it is only necessary to open the door of the lamp-house and swing the new lamp into position. « « « The Simplex equipment has a removable lamp carrier so that only one lamp is in the lamphouse. An additional holder is supplied for the adjustment of a spare lamp and changes can be made almost instantly. The Simplex lamphouse equipment will accommodate the 600, 750 or 1,200 watt Mazda lamp for motion picture projection, thus making it possible to change the size of lamp without going to the expense of changing equipment. The mechanism is so designed that it can be installed in the regular arc lamp housing. The Enterprise Optical Co., Chicago, 111., have placed on the market a lamp-house mechanism which is designed to fit any Motiograph projector, and is suitable for the 600-watt Mazda lamp. This deyice uses the same control moyementa for focusing as are used with the arc lamp. The socket is removable, thus providing for the quick replacement of a lamp. A modification of this equipment which is adapted to be fitted to any style of arc lamp mechanism has also been developed. ♦ « » Another lamp-house mechanism known as the Sheck Universal Adapter has been developed by the Argus Lamp & Appliance Co., Cleveland, Ohio. This equipment is intended to be univerial in application; that is, it can be used on any existing motion picture machine. It is necessary only to remove the condenser holders on the front of the lamp-house and bolt the small adapter, which carries an incandescent lamp, to the front of the regular lamp-house. The adapter carries a condense!" holder on the front of the house, which is fitted for two sets of condensers— one condenser is of the Corning corrugated type and is for the projection of motion pictures. The other set of condensers is of th« usual plano-convex type and is arranged to b« slipped into place when slides are to be shown. Another adapter is being developed which will care for the 750 and 1.200 watt lamps. By the use of the Sheck Adapter any machine can quickly be converted for the use of Mazda lamps. Interchangeability of lamps is obtained by using a removable lamp carrier in which the lamp is adjusted — two lamps can be adjusted and one is then ready for use in case of an emergency.