Canadian Moving Picture Digest (Apr-Sep 1918)

THE PHYSICS OF LIGHT Third of Study Series (Continued from laat week) Pure white light is termed the visible spectrum or rather those colors that white light are composed of from the deep red to the violet end. Now infra-red light is those rays of light that lie between the deeper reds and the long heat rays, and is invisible to us. Ultra-violet light is those rays that lie beyond the last visible rays of violet, and is likewise invisible to our eves, So you will appreciate the fact when I say that these invisible, or, as they are sometimes called, “dark light,’’ has nothing to do with a projected picture, but like many other things, must be learned in connection with one’s profession. They have no direct bearing on the actual work engaged in, but it is necessary to be acquainted with these facts in order that your education in your profession may be complete. Now to show you how this works out in practice. How many of you have, or are using, the ‘‘ Amber Lux Lens’’? I venture to say that there are many thousands used in America, yet I am doubtful if two per cent. of these users are acquainted with their action correctly. It is said by some that they absorb and prevent ultra-violet light, which is extremely harmful to the eye, from reaching the screen. This is not so. for no ultra-violet light has never yet left the lamp house by way of the condensers. There are other theories by the score advanced by the operator as to the action of these ray filters, doubtless most are incorrect. So it goes on down the line of miraculous happenings and their causes, effects, etc., more than likely only guessed at. Then the principle of absorption comes along. I have on any number of cases asked operators if all of the light that strikes the surface of a lens passes through it. They may admit that some reflect, but that is all. They never consider the absorption that takes place. It may surprise some to learn that an acerage condenser absorbs approximatelv 28 per cent. of the light that passes into it, to say nothing of the reflected light from the surface. You can readily understand the importance of a certain amount of technical training in matters projectional, and the more the better, and combined with good practical experience makes you the highest order of an operator. Then to give yourself a test I will PROJECTION CANADIAN MOVING PICTURE DIGEST. DEPARTMEN give you a few everyday questions on light action, and see hoy many of them you can answer yourself. They are sure to interest you, ‘and you will be able to answer all of them if you follow tho studies through. How can a beam of light be bent? Why does not winking the eye interfere with vision? What is the reason for the dazzling whiteness of the snow? What is white light composed of? What becomes of the energy of light when light is absorbed?) Why can you not see the individual spokes of a wagon wheel in motion? Why can you see these individual spokes when there are only one or two! In looking at a motion picture wherein is shown a wagon wheel moving, why does it sometimes look as though it were turning in the opposite or backward direction, and sometimes seems to be standing quito rigid? The answer to these questions come from only a technical study, and that is the object of these studies, to interest you. ON LENSES. The object of a lens is primarily to change the path of a ray of light in another direction. We have found that all transparent liquids and transparent. crystalline substances possess this power, and this action is termed the power of refraction. And the extent to which the path of the ray is changed is called the refractive index of that substance. The refractive index is then calculated by the degre of angle taken by the Hight ray, and a mathematical value is then given to the substance in question. This is a simple generalization to express the refraction principle. In working out refractive values of different substances certain kinds of glass were found to be of the greatest value for the construction of lenses, in England an invented process embodied a secret way to make erystals in which was enclosed pure water. By reason of the fact that water had such a low volatilization point (boiling) very often the Phone College 7262 WM. P. COVERT BUSINESS REPRESENTATIVE MOVING PICTURE MACHINE OPERATORS LOCAL Neo. 173 Canada Toronto, Page Seventeen dutedby ~*'ISI Conducted by Mr. C. A. MCMAHON : lenses burst or split open, and this idea of water lenses was discontinued, although there are even as yet water lenses in cxistence. Then by use of a lens we find that the incident path of a light ray may be diverged by a refractive medium. We construct a lens first to converge a num. ber of light rays to a common point. This point is the focal point of the lens, and when a pin point of light is the source, then the point of foeus aud the light source are called the conjugate foci, meaning the two points of focus of a lens. Then we come to the opposite quality, namely, the dispersive or spreading power of a lens; that is to spread the light rays over a field greater than the field covered by the incident rays, The continuation of this article will be given in the next issue, and will deal with the first principles of compound lenses. ‘“‘THE EAGLE’S EYE.’’ ‘“‘The Eagle's Eve,’’ the great patriotic serial, which exposes the German spy menace upon the American continent, is placing a big advertising and * publicity campaign before the Ameri can and Canadian public, this serial. The serial, which is being distributed in Canada by Superfeatures, Ltd., is said to be highly educational as well ag full of punches. In conjunction with the serial in Canada, announcement has been made that the story will run serially in the Toronto Star Weekly and the Montreal Star. These are two of the representative newspapers of Canada, and doubtless will do much to popularize ‘‘The Eagle’s Eye’’ with Ontario and Quebec movie fans. to promote PARALTA PLAYS POPULAR. Paralta Plays have received a wonderful reception at the hands of the Canadian exhibitors. They have been truly named ‘‘The Pick of the Pictures.’’ Regal Film Limited are anx ious that those Canadian exhibitors who have not as yet become acquainted with this splendid brand of pictures, get in touch with the nearest Regal branch, as some mighty interesting arrangements can be made to play ‘‘A Man’s a Man,’’ ‘‘His Robe of Honor,’’ ‘‘The Turn of a Card,’’ and ‘‘Madam Who?’’ Such stars as Henry B. Wathall, J. Warren Kerrigan, and Bessie Barriseale are offered. They are great boxoffice attractions in the Dominion. ml “THE SCREEN PAR-EXCELLENCE” ACME GOLD FIBRE SCREEN Manufactured by GEORGE McARTHUR, Ur. Google WINDSOR, ONT., CANADA