Motion Picture Herald (Apr-Jun 1931)

June 2 7. 1931 MOTION PICTURE HERALD 49 I^^SCLND CEDC€DIJCTI€N The BLUEBOOK School Answer to Question No, 83 By F. H. RICHARDSON BLUEBOOK SCHOOL QUESTION NO. 88— (A) Explain fully iust what various things sound reproduction systems do. (B) Generally speaking, how many times Is the impulse from the photo-electric cell amplified before it reaches the horn receiver? (C) What is the essential requirement of sound sprocket action and what is essential In the matter of Its care? (D) Exactly what would be the effect of the adhesion of anything to the face of the sound sprocket, no matter how slight Its thickness might be? The question was: {A) Exactly what amount of space on the film does the slit beam illuminate? (B) Is the light from the slit of unvarying brilliancy when it reaches the film sound band? (C) What happens to the beam of light after it has passed through the sound track. {Apology. That was wrongly worded. It shotdd have read, what happens to the beam of light as it passes through the sound track? — Ed.) Is it still of unvarying brilliancy? (D) What will the light beam on the photoelectric side of the film be a reproduction of, in so far as concerns its brilliancy? The list of correct answers grows gradually longer, as also does the list in its entirety. Those answering correctly were : Herman B. Billings, Lester Borst, C. Rau and S. Evans, George Thompson, Billy Rankin, George H. Artley, R. D. O'Brien, Sam C. Small, Tom Hobart, E. L. Banning, D. H. Macy, H. G. Shelton, Thos. Dunbar, Robert b. Starr, H. Howard, Chas. G. Davidson, Samuel G. Bird, Ben I. Teeters, Toot Lavenburg, Dick T. Bann, R. L. Rallins, Tom Davis, L. V. Jarvis, Andrew Schaefer, T. Ackton, D. L. Mitchel, Bill Doe, F. C. Sanders, A. T. Rogers, Richard Lewiston, Donald Lomax, F. K. Post, Henry Boylson, W. Wilkens, Dan Tomlinson, Tom Alexander, G. L. Doe, Frank E. Brunnage, Andy Birdsal, K. T. Shane, F. D. Richards, David Overmyer, G. M. Myers, Lewis Lewis, Robert Fortell, M. C. Cummings, J. D. Daniel, Peter Oak, D. L. Michel, Joe Simmons, James McGuire, G. T. True, Abe Rassenberg, R. Peters, Benjamin Shawnison, Frank T. Marion, Robert Alexander, P. H. Haynes, D. L. Haynes, L. Anderson, Sam L. Brandt, Roger Wynne, Dan Hughes, B. L. Adams, Thomas J. Ryan and John Steele. The following sent especially excellent answers : Evans and Rau, George H. Artley, Herman B. Billings, Lester Borst, Dick T. Bann, George Thompson, G. L. Doe and Frank T. Marion. I believe in this instance the answer of G. L. Doe is best suited to publication. He says : "The slit illuminates a space on the sound band .080 of an inch wide by .001 of an inch high. This is presumed to be sufficiently thin to bring out the various modulations of sound and to avoid all possible confusion caused by illuminating two sound modulations at once, though of course since these modulations more or less run or shade together, this cannot be entirely avoided. "(B) The light is of unvarying brilliancy when it reaches the plane of the sound band, though of course if the exciting lamp filament be either sagged or out of proper adjustment there would be variation of brilliancy along the length of the beam. However, regardless of that, the brilliancy at any one point in its length would be unvarying. Perhaps, though, I have not quite made my meaning clear. In all this I refer to the light, which actually strikes and passes through the slit. "(C) When the light beam passes through the film track it is stopped, or partly stopped, according to the density of the sound band at various points, or in the variable area track, in accordance with the variations in transparent area. This causes the beam to have variations in brilliancy after it has passed through the sound track. It is no longer of unvarying brilliancy, though of course owing to the tremendous speed of light it perhaps cannot be said that any variation in brilliancy actually exists in the beam between the film and the P E cell. The action is too rapid for that, but the brilliancy is constantly varying. That's Something! A letter to ERPI from Colonel H. E. Cloke, commanding officer of the 16th Coast Artillery in Honolulu, at Fort Ruger, tells of a recent target practice and its effect on Western Electric sound apparatus. "During the practice," states the letter, "the windows of the film booth were unintentionally left closed and the concussion broke two window panes. The concussion at the same time caused damage to some of the other buildings. No extra precautions were taken to protect the sound apparatus." At the film showing that night, concludes the colonel, the sound apparatus functioned as well as usual. nevertheless. That is what enables us to reproduce sound. "(D) The brilliancy of the light of the beam after it has passed through the sound band represents the sound values contained in the sound track through which the light has passed." There, gentlemen, I believe you will all agree that is an excellent answer. My compliments to Brother Doe, of Chicago. AAA ARC TROUBLE Gray Phillips, Crescent theatre, Grand Haven, Mich., presents an interesting problem. He has Motiograph, DeLuxe model H. projectors, equipped with Motiograph reflector lamps, using 25 amperes. He loses the arc about once every four hours and, so he says, for no good reason at all. Everything runs along O. K. and then suddenly the arc goes on strike, usually about 10 minutes after starting a reel. He says : "I have checked everything I know of to check, including line voltage, which varies from about 108 to 115. Resistances are O. K. No loose connections and proper amount in circuit. Arc gaps are from three-sixteenths to one-fourth inch long. The feeding motor runs free and is every way in good condition. No loose connections. Carbon trims crater vertical and horizontal (don't know what you mean by that: Ed.). Carbon jaws are clean and the connections are tight. Generator voltage 80, almost constant. Carbons dry and free from cracks and defects. Both lamps behave the same way. Sometimes they will run along for two or three days, then I will lose the arc at frequent intervals. Can you help me?" I am afraid I cannot, though it seems to me, if all you have said is correct, the trouble may be loose cores in the carbons. There have been some complaints of carbon core trouble, which doesn't appear in all bundles of carbons. Suppose you see if the trouble shows up immediately or soon after you have opened up a new bundle of carbons. If there is very little voltage variation and everything else is all right, it seems to me it must be in the carbons. Be sure, though, that the feeding motor maintains an even arc gap at all times. These are the only two things I can think of. If any one else has had the same experience let him address Mr. Phillips.