Moving Picture Age (Jan-Dec 1920)

Mav, 1920 MOVING PICTURE AGE 23 Proj Any questions pertaining to projection of films and slides ■ g^g^^'4r^ g^'f^ on the screen will be answered by this department. Address | C X-^ IX V-l Ax "Projection," Moving Picture Age, 418 So. Market St., Chicago | If an answer by mail is desired, enclose stamped envelope. | iiiiiiiiiiiiiiiiiniiiiiiiiiiiiiiiiiiiiiiiiiiiii iiiiiiiiii imiiiiiiiiiiiiiiiiiii iiiiiiiii iiiiiiiii iiiiiii nil iiiiiiiiiiiiiiiii iiiiiii iiiiiiiiiiiiiiiiiiiii iiiiiiiiii iiiiiiiiiiiiiiiiniiiiiiiiiiiiiiii mi liiniii mi ii mimiii i miiiiimiiiiiiiiiiiiiiiiiii For the Amateur Projectionists By Donald R. Burgess Motion picture projection in schools and churches is now not only possible but decidedly practical. Fair results may be obtained from portable projectors by even inexperienced persons, while splendid if not professional results may be had if one thoroughly understands the machine he is using. By understanding the machine I do not mean merely knowing how to "thread up" and turn on the light. I mean that every one who has anything to do with the projector should know the principle on which it works, what each lens is for, and the construction of the lamphouse, mechanism, and motor, if there is one. The lamphouse should be taken apart and the adjustments studied. Then the bulb should be examined. On the low voltage, high amperage bulbs a small filament is used called a maximum concentration filament. This must always be placed in the lamphouse in such a position that the filament will present as much surface to the condenser as possible. With projectors having an adjustable reflector, too much care cannot be taken to center it exactly. Some portable projectors have no adjustments, the lamphouse being permanently assembled to meet all conditions. If there is a door on your lamphouse be careful not to open it when the condensers are heated unless you are sure that no cold draft will blow on them, for they crack easily. Do not take the mechanism to pieces unless overhauling or repairs are necessary. It is not Tiecessary to take it apart in order to study it. If the mechanism is protected by a covering, take this off, but leave the gears alone. Fasten the crank to the machine and slowly turn it, following out the course of motion in the gears. When you have seen the use of each wheel, put a strip of film in the machine and follow its movement over the sprockets. See if you can find the relation of the shutter to the movement of the intermittent sprocket. The motor need not be closely examined, as it is a separate piece of machinery and requires little or no care or adjustment. If at any time there is undue sparking at the brushes take the motor to an electrician for adjustment. The lens in any projector should be treated with great care. Most machine users are extremely careless with their lenses, "handling the glasses freely as the tube, and cleaning it . with the first thing that comes handy, even though it be dirty waste. A lens should be cleaned only with an old, soft piece of linen, after first breathing on the glass. Never touch the lens with your bare finger, for no matter how clean it is, it will leave a mark that will never come off. One point in the care of all projectors that is usually either overlooked or overdone is lubrication. A very little oil in the right place often enough is the formula for lubricating all projectors. In most cases the intermittent casing needs the most. Never put enough anywhere to make the entire machine greasy and even spatter grease on the film. The subject of who is to be allowed to operate the projector is a hard one. In schools, the entire faculty should learn the use of it. The man from whom you purchase the machine will gladly explain its operation at a faculty meeting when you first purchase it. It is to his advantage to do so. The teacher, however, cannot always operate the machine. At times she must be at the screen lecturing and pointing out the important parts of the picture, so it is well that a few boys be instructed in its operation. The scheme used in a few churches, and I think it a good one, is to license a few boys to operate it. This licensing may be the result of a competitive examination ; the examination to be given by the principal or pastor. The boys who are interested enough to work for such a license may with all safety be allowed to operate the projector. There are several good books on projection that anyone having to operate a machine will do well to study. With me the study "became all-absorbing. I do not know of many fields that offer such a scope of subject, all of them interesting, as professional projection work. The teacher or pastor who uses the portable projector must not forget the element of danger connected with the exhibition of standard motion picture film. Don't forget that the film is dangerous even when out of the projector. Keep it protected by a metal case and out of harm's way. And above all things, never leave the room when the projector is running. Lastly, and probably of more interest to the pastor, come a few of the finer points of the art of projection that should not be overlooked. It would not do for a church, often showing to critical, and at first decidedly skeptical, audiences, to start the film out of frame and with the picture slanting on the screen. Or if you use a stereopticon do you show slides that look more like the work of a finger print expert than attractive pictures or announcement slides? I have a saying of my own whereby I can gauge the ability of any projectionist, anywhere. It is this — "By their slides shall they be known." * ♦ * By W. R. Rutledge The field for mazda lamps in projection work has steadily and consistently increased during the last few months and there are many former skeptics who have revised their opinions concerning the working of the high efficiency mazda lamp as a potent factor in this field. Today there are several types of apparatus being manufactured for the purpose of affording a suitable medium for such projection. There are two main systems used in mazda reflection. In one of them the use of the piano convex condensers is retained, while in the other the corrugated lens is introduced. One advantage claimed for the latter is that it breaks up the image of the filament coils and thus produces a more uniform illumination on the screen. Judging by various experiments made by the writer this claim is a little too strong. An image of the filament coils can be and is produced on the screen even though the corrugated lens is used. This image can be "filled in" by proper use of a reflector behind the lamp if great care is exercised in placing the reflector in such position relative to both distance from the filament and angle of reflection as will best serve to eliminate the objectionable image. No system is perfect and no conditions can be accurately defined that will bring the same results in all cases. We have in mind today one very large corporation whose engineers are the authors of a handbook on projection. In this handbook we are informed that because of the steps, or corrugations on lenses of that type, they are not suitable for projection purposes, the shadows cast by the corrugation being very detrimental to good projection. It is a fact, however, that a majority of the projection machines brought out during the last year are equipped with lens of this type. Condenser lenses are frequently used in pairs ; one to collect the light from the source and the other to pass it through the film to the objective lens in front. Both systems of condensers have many friends whose opinions differ according to the square of their experiences. One advantage in using the corrugated system lies in the fact that in all apparatus using that style of lens there is usually a fixed distance from lens to film, and the operator cannot vary or change it in any way. Very often he cannot change to any appreciable extent the distance between the filament of the lamp and the lens, while the chances of changing or interfering with the distance from filament to reflector are very remote ; consequently the entire apparatus either "works" or is discarded because it "won't work." The advantage of using the piano convex or the meniscus bi-convex lenses is worthy of attention. Where this lens system is used care must also be taken in spacing the optical elements very nearly according to the following dimensions : Back of mirror to lamp filament should be five inches ; from the filament to the face of the rear condenser face, three and one-half to three and three(Continued on page 25) Gold Fibre Screens For Mazda or Arc Light Have power of expression greater even than the most forceful delivery of words. Distributors from coast to coast Samples and literature upon request. MINUSA CINE SCREEN CO. St. Louis, U. S. A. rsCREENs BUILT BY] 8RAIN5