Motion Picture Herald (Apr-Jun 1931)

April 11, 19 3 1 MOTION PICTURE HERALD 47 SOUND CEPC€DUCT1€N The BLUEBOOK Schoo Answer to Question No. 72 By F. H. Richardson THE question : Tell us exactly what the conscientious motion picture sound projectionist who expects to get the best possible results from the horns will do every day with reference to the exciting lamps. Tell us just what will happen if the exciting lamp filament is sagged. Explain why this effect will be brought about. Tell us just what the effect will be of using an exciting lamp which has discoloration on the interior of its globe. Tell us just how you would proceed to test the sidewise adjustment of the exciting lamp filament image at the sound gate aperture. Here are the names of those submitting correct answers out of a total of 793 replies : S. Evans and C. Rau, Herman B. Billings, Earl Boyer, Leslie Yates, A. R. Reisman, Wm. Gibson, John Doe, Frank Mitchel, R. P. Franklin, George Anderson, G. E. Doe, Andy Richards, R. B. Whitnah, Wm. Borlson, Tom Turk, S. Kliene, Lewis Henderson, L. D. Herbert, Alex Smith, T. L. Woods, Robert Dodson, Frank Gibson, S. Cimms, R. P. Franklin, T. Van Vaulkenburg, R. D. Albert, C. Daugherty, Harry Crowley, John Katarch, George Thompson, George Peterson, Thomas Peters, L. L. Hays, D. R. Martin, F. C. Richards. Albert Rowan, Tom Simpson, Robert D. Edwards, T. L. D. Peters, Harry Sommers, Wm. U. Tinney and Edgar D. Wilson. AAA Of all these I have selected the anwers of Evans and Rau, Billings, Boyer, Dodson, Henderson, Turk, Van Vaulkenburg and G. E. Doe as best, and from them I have selected the reply of Tom Turk for publication, though the eight named are essentially even in quality. Here is what brother Turk says : "The projectionist who proposes to get the best possible results from his sound apparatus must pay very close attention to certain things concerning the exciting lamp and its optical train. First of all, each day before starting the show he must examine the exciting lamp critically, making sure that (a) its globe is perfectly clean inside and out; (b) That its filament is perfectly straight; (c) That the lamp is in perfect adjustment so that the focus at the slit is correct in all details. He must make sure that it is making good electrical contact. He must check up and know that the exciting lamp current value is just what it should be. If too high the lamp will not last through its rated period of life. If too low there will not be sufficient sound volume, except at a too high fader setting, and perhaps not even then. Also if the exciter lamp current be too high I have found the fader action to be unsatisfactory — too sensitive. Simplifying Sound RCA Photophone this week issued to the trade a "Handbook for Projectionists," a 215 page, splendidly presented nnanual in which appears a comprehensive description of its apparatus and the elementary fundamentals of an understanding of its operation. In addition to explaining the "how" and "why" of Photophone operation, RCA "aims to give this information in such a fashion as to enable the projectionist to intelligently recognize, locate and remedy such minor defects as might occur during the operation of the equipment, and make whatever minor adjustments which may become necessary." "If the exciting lamp filament be sagged, then of course its image at the mechanical slit will also not be in a straight line, and since the slit itself is a straight line, the two cannot be made to match properly throughout the slit length. The result will be loss of volume and to a certain extent sound distortion. AAA "Discoloration on the interior of the exciting lamp globe results, of course, in light absorption, hence loss in sound volume, provided such discoloration is low enough to be opposite the filament. Discoloration begins at the top of the lamp and gradually works downward. Also such discoloration results in tonal injury, because of the impurity of the light which is not so 3,bsorbed. I am not altogether certain as to this latter, but believe it must be true. I have talked with our service engineer concerning this point. He also would not express a positive opinion, but is of the opinion that the effect would be set up." (Your editor also is not entirely certain, but like the service engineer and brother Turk, believes tone quality would be injured by globe discoloration, for the reason that surely a certain amount of color would be added to the light by the deposit it must pass through. F. H. R.) "In order to test the sidewise adjustment of the jamp filament at the sound gate aperture • . ." No, we will stop right there. The answer of friend Turk to this particular item is to some extent faulty. Sorry, but that is the fact. I have therefore concluded to substitute the answers of Evans and Rau and Earl Boyer to this phase of the matter. Here is what Evans and Rau have to say : "To test the sidewise adjustment of the exciting lamp filament image at the sound track, secure a piece of negative film and thread same through the sound gate, with the emulsion side toward the light. Then light the exciting lamp and allow the light from it to shine on the film while slowly counting to 10. Then turn the flywheel of projector until the film has moved about a fraction of a sprocket hole. Repeat the count while light is shining on film. Do this several times. Then remove the film and there will be a series of lines on that part of the film whic hwas exposed to the light. These lines are imprints of the image of the slit. By cutting off a bit of sound film and comparing it with the test strip, with sprocket holes perfectly matched, it can be seen whether the sht image is correctly centered sidewise or not." AAA And now we will listen to brother Boyer, who explains thusly : "The sidewise adjustment of the exciter lamp: There are sound equipments that have a fixed sidewise position for the exciter lamp, hence this adjustment is not necessary. Other equipments require this adjustment and some sound heads are constructed so that this test can be made with the eye. In the front part of the sound head there is a hole through the housing in line with the slit in the lens system and the filament of the exciter lamp. The photoelectric cell is removed and a piece of very dark film is placed in the sound gate, the exciter light is turned on. Now you can look th rough this hole in front of the sound head and see the image of the slit on this dark film that is over the aperture in the sound gate. The exciter lamp is now moved sidewise back and forth until a position is found where the image will be the brightest. The adjustment is now cornplete and the exciter lamp's filament will be in perfect line sidewise with the aperture in the sound gate. The image will have a uniform brightness all the way across the sound tract. There are other ways to make this test, but I have found this method to be more practical." Would be glad to have the comment of some of you chaps on just what you have found to be the most practical method of sidewise adjustment. BLUEBOOK SCHOOL QUESTION NO. 78: Should the theatre manager or projectionist feel obliged to alter the horn setting without the assistance of a service engineer, what should be done first? What is the best sound projector location? Tell us just how you would proceed to locate horns in a wide auditorium.