Movietone Bulletin (September 1928)

Projector Optical System (Continued from last issue) AST week we placed before you the importance of properly lining the various elements of the projector optical train. We set forth the possibilities for light loss through improper selection of condenser lenses and their improper spacing with relation to each other. Of course, it is granted that the straight are is rapidly passing out of the picture, and that the old style plano convex condenser will probably soon be found only where high intensity ares are used. Still it is best that you understand the possibilities for loss of light by improper procedure when they are used, for they still are with us to a considerable extent. The possibilities for loss where the reflector arc is used are not so great as they are with the plano convex condenser system, but they are considerable, nevertheless. The mirror of the reflector are light, regardless of the particular make of the apparatus, is presumed to be exactly of the curvature which will locate the light source the correct distance from it when the proper light concentration is had at the spot. The action of these mirrors may be the better understood by examining figures 315B and 315C, page 833 of Vol. 2 of your Bluebook, and by studying the text matter accompanying them. Also it is recommended that you study “Cleaning Mirrors,” pages 831 and 832. It, of course, will be understood that a mirror surface filmed with dirt, or “fogged” with deposit of any sort, cannot possibly be expected to produce maximum results in light reflection; moreover, such deposit aside from reducing the reflective power of the mirror, has a tendency to diffuse the light, as you may well understand, and diffusion inevitably means loss. It therefore follows that the mirror surface of reflector lamps must be kept scrupulously clean. Never assume that a mirror surface is perfectly clean merely because it looks clean to the eye. Clean its surface before each show in a twoa-day house, and twice a day in the continuous. It really is a small task to do this and wasted light means wasted. electric power, as well as a lowering of screen brilliancy. Use only a soft, perfectly clean cloth, or soft toilet paper for cleaning mirrors and condenser lenses. If the surface be cold and not visibly dirty, just breathe upon it and polish immediately. If a liquid is used, I would recommend denatured or wood alcohol, with a little water added to prevent too-rapid evaporation, as the surface must be wiped and polished while still damp. Caution: Do not permit the alcohol to get on the back of the mirror as it may injure the coating. True it may not, but there is always the chance. Next week we will consider the possibilties for loss at the spot. (Continued in next issue) Storage Battery Care IVE your storage batteries G daily attention. Test them with a hydrometer every day, following the directions in your instruction book, found under “Running Storage Batteries,” Instructicn Sheet No. 54, Issue April 25, 1928. It is very important that this daily hydrometer test be made, so don’t neglect it. Also, while it may seem a bit superfluous, still I will caution you that you mu:t never test the pilot cell after adding water. After adding water a reading would not be reliable until the battery had either stcod for quite a while, or had worked long enough to thoroughly mix the water with the battery fluid. Of course you know water must be added to storage batteries more frequently in summer than in winter—that is to say unless the batteries be kept in a room havng the same temperature summer and winter; also that water must be added more frequently if the battery is used constantly than if it be used for only one show a day. Probably it seems rather foolish to some of you to say that, but maybe it may not be at all foolish to say it to others. You never can tell, and the telling costs little. Incidentally, that last sentence is quite all right if you figure it out right. Read the instruction sheet before named carefully and fully. Follow | FLICKERS | Maybe you believe in fate and maybe you don’t. Fate is that thing which makes a street car break down the very morning after the boss has threatened to fire you for getting down late. Achieve fame and people will erect a monument to you. A monument is something they put up in public places for tourists to back up against and get their pictures taken. These days to save a girl from embarrassment you tell her that what would be her petticoat if she were wearing a petticoat is showing. If you want to learn, investigate things. The surest way to tell the difference between a toadstool and a mushroom is to eat it. An old-timer is a fellow who remembers how a woman sounded trying to talk with a mouth full of hairpins. Watch your step. A lot of fellows don’t know they are courting trouble till after they have married it. Don’t be rash. Rashness is the process of trying to do when you have six drinks in you what you said you’d do when you had three. Man is different from an automobile. He can’t get into high places in low gear. You can always tell who the big gun around an office is. He goes off about two o’clock every day and doesn’t come back. its directions religiously—that is unless you are looking for trouble, in which event you probably will find it. Particularly note the direction to never put a battery on charge unless it is down to 1200 and never permit a battery to get lower than 1190. Heed both those instructions or meet the trouble train in a head-end collision.