The educational screen (c1922-c1956])

298 Motion Picture Projection The Educational Screen Mr. Leonard Tovter, president of the National Association of Elementary School Principals, writes: I must mention what wonderful results we are getting with th« new TransLux Daylight Screen. . . . From now on we shall go right on with our pictures with better visualization than ever before, with all the curtains up and windows open. I regard the invention of this screen as one of the big steps forward in visual education. Darkened Classrooms Abolished ! The TRANS-LUX DAYLIGHT SCREEN can be used in daylight without darkening the room, thus avoiding poor ventilation and the expense of satisfactory window coverings. It can equally well be used with artificial lighting conditions when desired. The TRANS-LUX DAYLIGHT SCREEN is non-inflammable, can be cleaned and rolled up without damage. It is made in any size for any purpose. "Si And What Do Its Users Think? For the sake of finer and more economical projection, ask further details of Trans-Lux Daylight Picture Screen INCORPORATED 36 West 44th St. New York City And Rev. N e vir e 1 1 Dwigrht HiUis, nationally kno'wn as the pastor of Plymouth Church, Brooklyn, comments: At tlie beginning we were somewliat slceptical as to tlie results. ... I am writing not only to express my gratitude to you, but to say that without a single exception the lecturers and ministers who have used the screen, both at every hour during the day and again at night, pronounce it the best screen that they have ever used. It is quite beyond any words of praise. will, too, if you make use of it and let it help you. In this department I shall probably have cause to refer to the "Blue Book of Projection" more or less frequently, though I shall do so only when necessary, as many of you have no copy. Limitation of space here will often preclude full treatment of an important topic and the simplest method will be to refer you to an accepted standard text on the subject. Worn Aperture Tracks John R. Bollinger, Winnipeg, Manitoba, says: "I have a DeVry suitcase projector which I have had for a bit more than four years. It has been used quite a bit, but I have taken very good care of it, or have tried to. Used a good oil, selected and applied according to information in the Blue Book of Projection and former editions of the same, all of which I have. This projector is used both in my home, in the home of my friends and in business. It seems to be in excellent condition. I am unable to detect anything wrong with its mechanism, but of late the picture has a tendency to blur in the center occasionally. By this I mean that while the picture will be perfectly sharp all over, it will suddenly blur in the center. Then it may (or may not) get sharp again almost immediately. Can you advise me as to what is wrong?" Your trouble seems to be rather obvious: A lens works on certain definite focal points. If the object of which it is to form an image is a certain distance from its optical center it will focus the image a certain definite distance on the opposite side of its optic center. Suppose the film to be three inches from the optic center of the lens, and the image thirty feet, or 360 inches on the opposite side. It will be readily understood that a very slight alteration in the shorter distance will mean a considerable alteration in the larger one, the proportion being 120 to one. In this connection see figure 36D, page 146 of the Blue Book of Projection. In all human probability you will find, by careful examination, that the tracks of your aperture plate have become worn, which causes the film to "buckle" as it passes the aperture, hence not always to lie fiat. This has the effect of altering the distance of portions (particularly the center) of the film photograph from the lens, the efifect being to throw that portion of the picture out of focus. You should have a new aperture, which you will be able to obtain from any DeVry projectors, or from the manufacturer direct. His address will be found in his advertisement. I would suggest the advisability of sending the entire mechanism in to the maker for a general overhauling. You have had it four years. It deserves attention. F. H. R, WANTED— Discarded Safety Films States Trading Co., 27 Third Ave., New York FOR SALE One Pair Simplex Projectors 1921 Model One Pair Powers 6 B Projectors 1921 Model One Pair Powers 6 A Projectors 1918 Model One Pair Motiograph Projectors 1 91 7 Model All of these machines are factory rebuilt and guaranteed, furnished with either Mazda or Carbon Arc. The Theatre Supply Co., Film Bldg., Cleveland, Ohio