The Moving picture world (May 1922)

May 6, 1922 MOVING PICTURE WORLD 97 PROJ ECTION % F.H.RICHARDSON Many Problems in One The Central Amusement Company, F. O. Buchannan, manager, Bristol, Va.-Tenn., wants advice, as follows : Have a house seating 350, in which have been using A. C. It is my intention to install a 60 ampere Westinghouse rectifier. Projection distance is 100 feet. Expect to use a 7-inch E. F. projection lens. Screen is a genuine mirror screen. Question is what condensers should I buy, and how far apart should they be spaced. Will the Gundlach be large enough in diameter, working under these conditions? Do you think 50 amperes will be too much, or would you advise me to install a dial switch on rectifier and reduce amperage? If I did this would it mean a saving in current? What we want is the best possible lens combination under the working conditions. A Gundlach is about as high as I can afford to go in price. Figure on getting Paramount condensers. A Thirteen Foot Picture Your 7-inch E. F. projection lens will give you approximately a 13-foot picture at 100 feet, and will probably have about a 5 inch working distance. Whether 50 amperes would be too much would depend somewhat upon what type of surface your mirror screen has. If it is a "Satin Finish," which is a screen designed to work in a narrow house, then 50 amperes D. C. will give you a very brilliant picture, PROVIDED you have your crater at an efficient angle with your face of the collector lens, and PROVIDED you have your lens system intelligently selected and adjusted. Possibilities for light loss or waste are so many and so very great that it is difficult to give advice. Often I tell a man what to do. He kicks that the advice did not work out, and after much trouble I find that he is working unintelligently in other directions. Forty amperes with a 55 degree crater angle will deliver more light to the spot than will 50 with a less efficient angle. A spot of IJ^ inch diameter puts very much more light through the aperture than does a spot two inches in diameter, and delivers to the projection lens an astonishingly greater amount of the total light falling upon the spot. This will be made very clear in the new handbook. Then, too, if you are getting all the light possible through the aperture, but the projection lens is picking up only a part of it, there again is waste. So you see, such things depend upon so many elements that I often hesitate to give advice unless I have reason to believe that the inquirer knows his businss as a projectionist very thoroughly. My advice may in itself be perfectly good, but if he kills it by unintelligent work in another direction HE INVARIABLY BLAMES ME I Not An Insinuation This, Friend Buchannan, is NOT an insinuation that I believe you do not know your Notice to All PRESSURE on our columns is Buch that published replies to questions cannot be guaranteed under two or three weeks. If quick action Is desired remit four cents, stamps, and we will send carbon copy of department reply as soon as written. For special replies by mall on matters which, for any reason, cannot be replied to through our department remit one dollar. THE LENS CHART Are You Working by "Guess" or Do You Employ Up-to-Date Methods? You demand that your employer keep his equipment in good order and up to date. He owes it both to himself and to you to do so, but you owe it to him to keep abreast with the times In knowledge and in your methods. The lens chart (two In one, 11x17 inches, on heavy paper for framing) is In successful use by hundreds of progressive projectionists. "Don't guess." Do your work RIGHT. Price, fifty cents, stamps. Address Moving Picture World, either 516 Fifth Avenue, New Tork City, or 28 East Jackson Boulevard, Chicago, 111. business. Not at all. It is merely a general discussion of the difficulty of giving advice where the results depend upon so many equations. In the sketch I have laid out your system roughly — not accurately, but roughly, mind you. It is pretty nearly right, however. Assuming 50 amperes, you will need a collector lens and a Tyi converging lens, with about 17 inches from center of condenser combination to aperture. I have assumed a five inch working distance for the projection lens, which may or may not be right, but should be nearly so. In the drawing I allowed 17 inches from face of condenser to aperture. It should have been about 16, the 17 being from center of combination. The result shows a 2% inch diameter lens picking up the entire beam, which it would not quite do as the correct distance is, as I said, 16 inches. I do not remember the exact free diameter of the No. 2 Gundlach projection lens, but the tube is 2 29/32 inche.^ in diameter, so I think you will be all right,^ J^ofar as ability of lens to pick up nearly the entire light beam be concerned. Condenser lenses should ALWAYS be placed just as close together as you can get them without actually touching each other. One sixteenth of an inch apart at point of closest contact is about right. By all means have a dial switch on rectifier. Reducing amperage saves current, yes. Try out the 50 amperes and use your own judgment as to reducing, remembering that a dim picture won't increase box office receipts, though, of course, a too-bright one is not desirable. Use common sense and judgment, asking your patrons' opinions on such things. Progressive Union Charles Purcell, secretary Local Union 303, International Association of Theatrical Stage Employees and Moving Picture Machine Operators of the United States and Canada (Phew — some considerable name) writes, under seal of the union, as follows: Wrote you March 15 ordering twenty handbooks for the members of this local, inclosing twenty dollars as deposit. To date have received no acknowledgement of same and am not sure you received the letter. Will you kindly let us know as soon as possible. Doubtless you are very busy on the new book and that fact is responsible for the delay. Best wishes from us all. That is what I call progressiveness. There cannot be many more than twenty members in the local. In fact, I believe the order is for every member of the local, and the prompt action in ordering a book for its members, even before the book is out, proves that the local is, as a whole, progressive. The action might well be emulated by many larger locals, nor is it a far fetched conclusion to say that a local has the more right to demand that its members own a book of this sort, the worth of which has been amply proven by years of test. I say this because a local surely has the moral right to demand that its members equip themselves with such things as will help enable them to give service creditable to the organization which seeks constantly to raise the wages of its members. As to the letter, its receipt has been acknowledged by the book department of the Moving Picture World. I have nothing to do with such matters. The local has been informed that there will be a discount for books ordered by the local in such manner. And that will hold good for other locals as well. SKETCH OF MR. BUCHANNAN'S SYSTEM This is merely a rough diagram to illustrate the principles involved Handbook Bulletin April 20. — I finished everything in connection with the new handbook. The last thing was the indexing and preparing and arranging the list of questions. I have prepared almost eight hundred and fifty (850) questions, which will appear under appropriate headings, in the back of the book, the page on which the answer will be found being indicated at the end of each question. This will be an immensely popular feature of the new book and one which will render it doubly valuable in that it enables the student to study intelligently. Questions pertaining to each subject are grouped under appropriate headings, as for instance, all questions having to do with motor generations appear under that general heading. There will probably be twenty-five pages of questions. The price of the book is finally fixed at six dollars. Better get your order in NOW unless you want it delayed, for a large number of orders are already in and more coming rapidly. I do hope the book will please you, for I've