Moving Picture World (Jan-Mar 1914)

8o6 T?TE MOVING PICTURE WORLD The Condenser Matter. L. C. LaGrow, Albany, New York, lands on Brother James, Camden. New Jersey, all spraddled out, as follows: The point raised by W. S. James is one of more than passing interest to me, and probably also to most progressive operators, I cannot see how this hypothesis has any foundation in fact. (Sic him Tigel Bow-wow-wow! Fireworks from Camden. — Ed.). Howe.-er, as we know, light must travel in straight lines until the medium of travel is changed, or, in other words, so long as the path of the ray is through a medium of equal density. James says: "Emerge in a straight line" (I take it he means emerge in parallel lines), "and do not begin to spread until * * • several inches from the lens." If the rays emerge from the front of the objective in parallel lines what would deflect them thereafter? I believe Brother James is led astray by diffused light and the fact that lenses reflect as well as refract light. The lens tube and machine head are always full of diffused light, part of which is reflected along through the lens factors and as this light strikes the lens factor from almost every angle, and since the angle of in■ cidence has to do with the ajigle of refraction, we have considerable unused illumination emerging from the objective lens, most of which is dissipated. Proof of this: Continue lens tube to aperture plate painting inside of continuation black and not having it exceed the lens tube in diameter, and then work the front of your machine head so as to eliminate as nearly as possible all unrectified light from the aperture and try your light on a piece of cardboard painted flat black. (Phewl O my! such a headache. — Ed.). It will be found that the cardboard screen is truncating a cone of light, the apex of which is the true focus of the entire lens system. (Hey there! Somebody quick catch my coat before he escapes entirely. — Ed.). Rays not nor nearly parallel. I believe brother James is entirely in error in his assumption with regard to the length of lens focus and the crossing of light rays. This condition may obtain in short ifoci lenses, but, as I understand it, the best compounds have their point of convergence built outside of the tube in the longer focal lengths. Whether the point of convergence is inside or outside of the tube can be determined by diaphraming down inside the tube and finding the focus from parallel rays of light. Should the point of convergence be inside the tube the image will show greater definition on slight diaphraming, owing to the lessening of spherical aberration. If the point of convergence be outside the tube the image will show loss of intensity so marked as to be convincing. Definition will be greater at first but will suddenly be lost on diaphraming. What I am trying to say (thank you, that's the dope. Ed), is that a lens compounded so that the point of convergence is inside the tube, i. e., between the factors, can be stopped down much more than one so built that the convergence is outside. Diffused and unrectified light causes flicker when the shutter is too far ahead of the lens, or at least that is my opinion. We would all like some sure way of matching our optical system, and I think that if you and the boys would dig into it we would soon have a way. I am trying brother James' plan on page 1540, December 27th issue. I wish to assure you gravely that the editor is, metaphorically, seated on top of the flag-pole on the Woolworth building looking down, and his stenographer is glaring out of the office window at him. Some words, my boy. some words. I do not think brother James meant to express the opinion that rays emerge from the objective in parallel lines; that would, of course, be manifestly absurd, since they would continue to travel in parallel lines clear to the screen. I am given to understand that Professor Wall is working on this problem, and that the results of his labor will he submitted to the department for publication, therefore I think I would rather wait than enter into an extended discussion of these points at this time. Personally without going deeply into the matter, brother James' plan appeals to me, and I am of the opinion that there is a good, deal in it too. Your remarks concerning diffused light are unquestionably correct, and, moreover, this diffused light does, under certain conditions, caijse travel ghost, or at least I think it does; but I am not going into this subject just now. In the first place the questions are occupying so much of my time and energy at present that I have not the necessary time to devote to the matter. Later on, if Professor Wall does not settle it Cor us, we will see what can be done. It is, however, encouraging to see operators taking up advanced questions of this kind. It would be especially interesting to have the views of Mr. Miller, Chicago, on this matter. A Watch. Maine sends in 25 cents with the idea of starting a fund to buy the editor ft watch, to be suitably engraved as coming from his friends. He wants to know if there has been anything about the Kinemacolor machine in the department, and if not, could I give him a description of the shutter, etc. He has something new in slides which he will contribute shortly. In the first place, brother, while I appreciate the spirit which prompted you to propose the watch business, still I feel amply repaid for my labor in the knowledge that I am doing you boys some good. Moreover, while as cents seems an almost insignificant sum, still it is a good deal to thousands of operators, and, therefore, I cannot encourage the idea. As to the Kinemacolor sutler: It consists of a regular shutter, the effect of which is the same as the shutter of any machine and, in addition to that, there is an auxiliary shutter which contains two colors of gelatine and it is the combination of these two colors which produces the colors on the screen. In order to give you an intelligent idea of this I would have to consume a great deal of space. The Kinemacolor machine was described once, but it was a long time ago; it would be quite a job to hunt it up now and, moreover, I don't think you could get the back number at this late date. As to your trouble with the No. 5, it is rather hard to say what is wrong, but, at a guess, it would lie in the toggle movement, which is probably badly worn. By "toggle movement" I mean the bar and gears on the left hand side, which make possible the framing of the carriage. Valuable Experiments. Fort Worth, Texas, writes as follows: First let me say concerning the Joke, page 45, January 3rd issue. Brother Sturgeon didn't say how he beat it up the street so fast that the paving blocks have not entirely cooled off yet, and secondly, as to that Photometry, page 47, January 3rd: I made the tests with a Weber photometer and wattmeter, both of which have been feloniously abstracted (stolen) from your humble servant since that time. It is the only portable photometer I know of. But arc measuring is just approximate, owing to the variation of the amount of light given out in one direction at any one time, this due to the variations of the quality of carbons, position of arc, and color of light. I find that with carbons giving off a greenish light a little more illumination is produced on the same wattage. Next comes a yellow or orange cast, with purple cast the least effective of all. I am now experimenting on the color of light, and expect in the near future to produce a greenish cast which will be so perfect that you could hold a piece of purple silk dyed with methol violet 6B and get the same shade or effort in daylight as is given by the arc light. I don't say I will succeed, but if I do it will well repay me for my efforts. Now as to the ammeter illustrated on page 45: I will give you a diagram of one that will work, although, of course, it is not very correct, especially in lower readings, due to hysteresis in the iron core. When the current to be measured is passed through the coil it draws the soft iron core D, which is pivoted at P. The needle E is fixed to C at P. The core is drawn into the coil against the force of gravity, W serving as an adjustment. W must have a set-screw to hold it in position. This is what would be called an electromagnetic pendulum ammeter, and is built something like the ammeter of early days. The greater the current in the coil the greater will be the deflection of the needle. The General Electric Company informs me that your tests, as recently set forth in the department, are approximately correct, and that endorsement has been published. My compliments to you. As to the ammeter: I know that sort of an arrangement will work, but whether or not it will work as well as or better than the one illustrated on page 45, I don't know. However, those things are worth experimenting with, because an ammeter in the operating room, placed right square in front of the operator, is to my mind an exceedingly important piece of equipment. As to the light experiments, we will be glad to receive your report when it is ready. If you can accomplish what you expect to it will be, it seems to me, a very important matter indeed. What Is It? C. J. Berger, Rochester, New York, writes: Although the titles of my films are in focus, the pictures are blurred, fo^gy and hazy looking. I had my operator change the condensers, using various combinations, but the trouble has_ not been vanquished. The machine is a Power's Six-A. The curtain is a plain canvas, one coated with alabastine. The current comes through a Bell & Howell iio-volt a.c. compensarc and the lens is a Bausch & Lomb; the throw is 90 feet, using 45 amperes. The machine is somewhat noisy. Could you suggest a remedy? In the first place the proposition you put up seems to be if not impossible, at least highly improbable. If all of your titles are in sharp focus then your pictures ought to be so too, except for possibly an occasional scene badly photographed or developed. I am inclined to think the^ whole business is out of focus, and that you don't notice it so much in the titles. Examine your lens carefully and see if it is not dirty, oily, or if there is not a faint finger mark. Take the objective lens apart and wash the lenses with alcohol, polishing carefully with a perfectly clean, soft cloth, being sure that you get them together again properly, as per Figure 146. page 36a of the Handbook. Possibly you have had the lens apart and it was not put together properly, or that one of the combinations is loose in the barrel. I am quite certain your trouble lies in the lens. As to the noise in the machine, I could not give you an intelligent opinion without having more complete information as to what kind of a noise it is. Possibly the machine is badly worn, in which case it should be sent to the Nicholas Power Company for repairs. I would refer you to the instructions on the Power's machine on pages 270 to 290, inclusive, of the Handbook.