The Moving picture world (November 1923-December 1923)

PIUDJ ECTION EDITED BY F. H. RICHARDSON MeasuringCondensers ^ . Wilbur J. Camlin, projectionist, Paramount Theatre, Connellsville, Pa., has the following to say : Have been a reader of your department for three years and am interested in the advancement of motion picture projection. I want advice upon a very simple, yet to me a perplexing question. The supply house in Pittsburgh where we get all our parts and accessories does not send the condensers we order. At present I am using a 6% -7% piano convex combination. The 6% lens seems much heavier than the other, and now that the preliminary explaining has been done I will get at the question which is bothering me, viz.: Is there any way in which I can measure a condenser to find its proper size? Please advise me through the department. I had the latest edition of the handbook (Bluebook) and gave it away as a present. Have sent my order for another. It Is, I think, the most complete work ever written on projection. Thanks for its help; also for the aid the department supplies. Friend Canilin, the fact that one lens is heavier than the other is as it naturally would be, since the piano convex lens is thicker than is the 7l/2, hence has greater weight of glass. See figure 32, page 134 of the Bluebook, or page 96 of the Third Edition for explanation. Moreover, you may find that the 6yi lens has a thick edge and the 7yi a thin one, or vice versa, which means nothing optically, except that there will be a bit more light absorption in the thickedged than in the thin-edged lens. See page 167 of Bluebook. It does mean, though, that there is unnecessary surplus of glass, hence added weight; also that the very thick edged lens won't fit the holder rigrtly, and in some holders will be held too high, so that its center will be above the optical axis of the lens system. As to measuring the lenses separately, 'which is what I presume you mean when you say "measure the condenser," there is no method I know of by which you can measure them with absolute accuracy, because of the great amount of spherical aberration contained in the beam from such a lens. You may, however, measure with accuracy so close that the error is negligible by following the plan described on pages 153-154 of the . Bluebook ; also they may be measured by the method described on page 151, which is as follows : Select a room with only one window, or else darken all windows but one, leaving this one open. On the wall opposite the open window pin a sheet of white paper. Hold the lense to be measured in front of the paper screen thus established, with its flat side towards the screen, and very carefully focus some DISTANT object, such as a building or tree, on the paper screen. Be careful to hold the lens as nearly as possible square with the screen. Having focused the object as sharply as possible, measure the exact distance from flat side of lens to screen. Next reverse lens so its curved side is toward the screen, re-focus the same object, and again measure from flat side of lens to screen. Add these two measurements together and divide by two. The result will be the focal length (NOT "size," Friend Camlin, but FOCAL LENGTH) of the lens under consideration, as closely as you can measure it by this process. If you have focused the object care The report of the Nomenclature Committee of the Society of Motion Picture Engineers was laid over until the Spring meeting. It is proposed to adopt "PROJECTOR ROOM" as designating the room from which pictures are projected, instead of "PROJECTION ROOM," as proposed by the Nomenclature Committee. The reason is that some producers call their screening room a projection room, and that is quite sufficient reason why the projectionist should stand clear, keep away and keep his hands off the name "projection room." I want a letter from every one of you who approves "projection room" and disapproves "projector room." One local, Rock Island-Moline No. 433, has officially endorsed "projection room" and objected to "projector room." I would like to see other locals come to life and do the same, remembering that the nomenclature adopted by the S. M. P. E. will become standard. Wake up, men, and show your interest. Write your endorsement of "projection room" on a separate sheet — as an entirely separate letter, which may be sent in the same envelope with another letter, it you wish. GET BUSY! fully the result will be near enough for all practical purposes. Glad you like the. book and the department, but remember that the book is NOT to lay up on a shelf, but to STUDY. A good plan is to start in on those questions in the back and learn the right answer to every one of them. Weaver Douser J. ML Jacobs, Box 484, South Boston, Mass., writes to ask the address of the maker of the Weaver Douser, described on page 870 of the Bluebook. Also what advantage I think accrues from its use. This illustrates the difficulties encountered in the making of a book. The Weaver device looked good and was practical. It seemed that something of the sort was needed to take the place of the various make-shift devices now generally used, so, on the positive assurance of the sponsors of the Weaver that it would be promptly marketed and vigorously pushed, I allotted space to it, since which I have neither seen or heard of either the Weaver Douser or its makers. The advantage of such a device as against the various arrangements now in use is dependability, efficiency and LOOKS. This latter is of importance in high grade installations. Replying to friend Jacobs' question as to the address of the makers of the Weaver, I have not the slightest idea where they now are or if they now are. Values It Highly Allen Potts, projectionist, Strand Theatre, Miles City, Montana, orders a lens chart and says : I just can't get along without your lens chart. Evidently he had the old one and knows how much it helped. The new one is really a wonder in its completeness. At the late meeting of the Society of Motion Picture Engineers, one of the engineers said to me: "Richardson, that new lens chart is a wonder. It works out to perfection." I am sorry I did not make a note of his name, for I am sure it was one of the optical men. Boulder, Colorado E. C. Caywood, projectionist, Curran Theatre, Boulder, Colorado, shakes his fist under the editorial nose as follows: Members of local 608 and the Boulder theatre managers read the article, September 8 issue, headed "Dangerous Outrage," with much interest. For ten years past I have been projectionist in this theatre. In all that time I have no recollection of any film fire, or "explosion," which has even so much as excited the audience of any Boulder theatre. I thoroughly agree with you that the pub* lication of such a misleading statement constitutes a dangerous outrage, especially in the magazine which I have subscribed to for a number of years because of its truthful projection department! (Wham! O golly, what a jolt! — Ed.). As regards shop-worn projection equipment, we have no such animal In our fair city. Here in the Curran I have two late type Simplex projectors, a G. E. series arc M. G. set and a Westinghouse mercury arc rectifier. The Isis Theatre projection room, which has been in charge of brother L. Brazda for a number of years, has two Motiograph De Luxe projectors and a Westinghouse M. G. set. Will you kindly print the complete article you have from a paper published in Boulder, or else inform me as to the name of the paper? I do not remember having read any such article In any of our papers. I begin to think friend Caywood is imbued with the idea that I've taken the truth by the neck and slammed its head against a tree — that no such article was published, and the worst of it is that I am unable to prove him wrong. For years I kept every bit of correspondence on file for a year. It was an immense job, took lots of labor and space, and not one letter in a thousand was ever referred to. Of late years I have retained only such letters, etc., as seemed to have probable value for future reference, which the Boulder matter did not appear to have. It therefore went into the discard.