Motion Picture Herald (Jul-Aug 1936)

one spot in the picture is illuminated or "scanned" at a time. We have seen that the spot so scanned is of extremely small area. We have seen that after the beam of light has been changed to electric current, traveled to its destination through the air or by wire and been transformed back into a light beam, it is projected on a screen. Understand clearly that hundreds of thousands of such "spots" must be placed on the screen to make up each picture, with all but one of them retained until completion of said picture by persistence of vision. Right here is the crux of the whole matter. It will be readily understood that no very large amount of light can possibly be forced through a point so very small as the area of the scanning beam, at its point of contact with the film, and that amount of light is all that is available. Now if the receiving screen be of equal dimensions with the scanned subject itself, a satisfactory screen brilliancy might be obtained. A quite acceptable brilliancy may be had, I believe, with a screen one foot square. But when we undertake to magnify the various "spots" to a size that will cover a theatre screen — well, we attempt the impossible, so far as screen brilliancy is concerned. Let us assume the scanned picture to be one foot square and the theatre screen to have 100 square feet — a very small theatre screen. Is it not evident that the light received upon the theatre screen will be one hundred times less bright than was the sum total of light impressed upon the picture itself? For this reason I have said that until such time (television engineers believe it some day will be, though admitting that it is wholly in the future) as a far more powerful device for picking up television pictures is discovered, the introduction of television into theatres is wholly impossible. I might add that in this opinion I am backed by very eminent television engineers. And now here is some interesting information I have acquired in consulting television engineers regarding this articlev Television is transported through air entirely by "short wave," and short wave is but very slightly affected by static. It would probably be right now possible to transport acceptably a television picture by air through a rather sharp electrical storm. Oddly enough that would disturb it but little, but automobile ignition raises hob with it, particularly that of large trucks and machines in which the ignition is faulty. Steps are being taken right now to secure shielding of ignition on autos. To my way of reasoning, some temporary competition might be offered by television (if it would offer any at all) if it became as accessible to homes as radios. Home receiving sets are indeed right now available, but only at a price in advance of $500, with a 5x7-inch picture the limit. It seems to me that such tiny pictures could not compete with the theatre. They could, in fact, be one of the best possible advertisements for motion picture theatres. As to projectionists worrying about television, while it is wise to post yourselves so far as possible, I would not do too much worrying about its being dumped into your hands as sound was — not for a good while yet. There are formidable problems to be solved before television can adequately serve theatre screens. WHY SCREEN ILLUMINATION FADES h. G. samuels of Boston, writes, "We are told that screen illumination is not nearly so bright at the edges as at the center, and that the fall-off is gradual from center to edge. We are assured that on all screens the central section is from three to four times as bright as the edges. If all this is true, will you favor me, and I am sure many others, by explaining why this is? I have asked several Boston projectionists, but to date none have made any satisfactory explanation." The reason why screen centers are brighter than are their edges is that all present day projector optical systems project almost the full brilliancy of the center of the light source to the screen, but all other light source zones waste a portion of their brilliancy on the cooling plate, and this waste is progressive as the center of the light source is receded from. Just why the eye is largely unable to discern the very great difference in illumination in various sections of the screen I am, myself, not able to understand, but am well convinced that at least a portion of it is due to the sharp contrast between the black or very dark colored border and the reflection surface itself. That this would have considerable effect in reducing the visibility of the fall-off seems fairly evident. How great the difference is may be viewed by examining page 126 of your new Bluebook of Projection, where you may observe that, whereas the central zone shows a brilliancy of 24.3 candle power, the next zone drops away to 13.6, and the outer one to only 5.9. Incredible but true! The measurements were made for me by an engineer than whom this great industry has no better— L. A. Jones of the Eastman Kodak Company. And now as to the practical demonstration. Thin some coach painter's black, ground in Japan, with turpentine. The materials are not expensive and may be had at any paint store. Be careful to get none on the back of the mirror. Paint the glass surface and let it dry. It may afterward be washed off with turpentine and after that with soap and water. The mirror will not be in any degree injured. In this paint, using a sharp-pointed toothpick, make several tiny holes, being sure to wipe the glass perfectly clean, which will require several toothpicks, used one after the other. Make these holes at different distances from the mirror center and at different points in its circumference. Also make them just as small as you possibly can. Strike the arc and you will discover that there will be a succession of spots of light at the projector aperture and that different portions of each spot will pass through the aperture. The farther away from the center of the mirror the beam comes from, the less the amount of each beam which gets through, and the more that which is wasted on the cooling plate. At the center you will probably find the entire beam to be passing through the aperture. This is an interesting experiment. It may, with variations, be applied to the condenser type arc, with approximately the same result. PANIC PREVENTION IN FILM FIRES the following letter just arrived from a city in Missouri : "I am the owner of three theatres close to this city, but outside its limits. In one of them I am having an argument with an official who insists that I do certain things that I regard as useless. I have always found your advice, which I have many times followed in past years, with benefit Snapshot sent in by Berry B. Simpson, projectionist of the Showed theatre in Ocean City, Md., showing the projection room of that house, which is managed by Mrs. E. S. Srrohecker. The projectors are Simplex, the sound Western Eletcric. Light sources are 30-30 mazda. "The projection room," adds Brother SimDSon, "is nothing elaborate, but our screen image and sound are best on the East Shore, bar none!" 28 Better Theatres