International projectionist (Jan-Dec 1947)

ture, subtract the E.F. of the lens from the throw in inches. Multiply the difference by 0.825. Divide the product by the E.F. of the lens. The result is the width of the picture in inches. Formula: 0.825 (A — F) W = F Before determining the actual height of the picture for those cases where effective projection angles greater than 0° prevail, let us examine the method of finding normal picture height; that is, the height the picture would have if the effective projection angle were 0°. It will be noticed that the calculation is analogous to that for picture width. Rule: To find the normal height of the picture, subtract the E.F. of the lens from the throw in inches. Multiply the difference by 0.6. Divide the product by the E.F. of the lens. The result is the normal height of the picture in inches. Formula: 0.6 (A — F) nnorm. — " F To determine the actual height of the pictui e : If the effective projection angle is greater than 0°, the actual height of the picture will be greater than the calculated normal height. The vertical extenuation, or lengthening, of the picture increases rapidly as the projection angle is increased, thus while the eye can hardly tell the difference in a picture projected at a 5° angle from one projected "on the level," a difference in the picture as the projection angle is increased from 20° to 25° is easily discernible. Moreover, the rate of increase of extenuation is influenced by the E.F. of the projection lens, the rate of increase being greater for short-focus lenses than for long-focus ones. Now, the actual picture height may be measured directly, of course, as in Method 1, following, or it may be calculated, as in Method 2. The latter method should commend itself to all projectionists. Method 1. Measure the height of the picture image directly by means of a tape measure. Screen masking should be ignored when measuring picture height. Method 2. Rule: To find the actual height of the picture: (A) Subtract the E.F. of the lens from the throw in inches. Multiply the difference by 0.6. Divide the product by the E.F. of the lens. Call this "Result 1". (B) Divide 0.6 by the square of the E.F. of the lens. Multiply the quotient by the effective projection angle. Add to the product the effective projection angle. Treat this result as an angular value and, by consulting the trigonometric table, find the secant of this angle. Call this "Result 2". (C) Multiply "Result 1" by "Result 2". This final result is the actual height of the picture in inches. Formula: 9 is the effective projection angle: theoretical "normal" height of the picture must be multiplied in order to give the actual height. The extenuation factor was included as the secant term of the formula for computing actual picture height, namely: H = 0.6 (A — F) sec (v)] + (v)] To determine "vertical extenuation" of the picture: The vertical extenuation, or elongation, of the picture due to the factors of projection angle and the lens E.F. may be defined as the factor by which the It will be noticed that this expression is independent of the throw; also that it reduces to 1 for an effective projection angle of 0°. The remainder of the projection and screen data can be completed without difficulty. Historical Development of Sound Film By E. I. SPONABLE Twentieth Century-Fox Film Corporation IV. FORMATION OF FOX-CASE CORP. A MILESTONE IN THE ART CASE and Sponable, on Jan. 29, 1926, visited the Warner Theatre (N. Y. City) to see a demonstration of Maxfield's Vitaphone. We all agreed that the showing was very good and of commercial quality. However, we believed that our own reproduction was better with regard to illusion and naturalness. In the W. E. system they were using the large public address system, thus accounting for the large range without distortion. Their loudspeaker was apparently of the horn type placed above the screen. After lunching with Mr. MacKenzie we returned to Bell Laboratories where we met Dr. Crandall and proceeded to Mr. Craft's office. Craft advised us that his men had only made a preliminary report .to him but it seemed that we had nothing in our system which would be of particular use or addition to the W. E. system. Craft, however, was reluctant to give up our system entirely and said he would like to know more about it. Inasmuch as the reproduction of the film was the real test, we suggested that W. E. send us some of their film, both voice and music. We could then reproduce it at Auburn and at least satisfy ourselves regarding the merits of the two systems. They did not care to submit some of their film already taken, and stated that they would take two numbers and send them up to us the following week. We then left the W. E. office and proceeded to Captain Ranger's office in the Radio Corp. building. We advised Ranger that we were now ready to go ahead with the talking pictures with them or arrange for licensing the use of their amplifier system. We asked him to bring these things to Mr. Adams' attention and arrange for a get-together to talk the situation over. Mull Patent Situation After leaving Ranger we stopped at the office of Mr. Gifford where we talked t J. Soc. Mot. Pict. Eng., April, 1947, p. 275. over the patent situation. He had already prepared an opinion regarding the de Forest and Ries patents, this opinion being that these patents were of questionable value. Our talk with h>m seemed to further his conviction regarding their questionable value, and he stated that he would send us the written opinion in the near future. Feb. 13, 1926: Case devised a way to avoid film splice marks by using graded opaque at the join. Feb.. 15 to Mar. 1, 1926: Case and Sponable discussed with Messrs. Whitney and Stone (a vice president of G. E.) the possibility of combining the Case system with the work of their inventor, C. A. Hoxie. G.E. engineers Robinson and Marvin came to Auburn and went over the Case system. They were very pleased with it. Stone, however, would not admit the Case system added materially to that of G. E., and no agreement was reached. Mar. 19, 1926: John Joy, who knew Sponable at Cornell, paid a friendly visit to the Case laboratory. Technically, he represented Courtland Smith who had just joined Fox Film Corp. Joy reported concerning the Case talkingpicture system to Smith, and the latter requested Case to bring his equipment to New York to demonstrate to the Fox people. Apr. 8, 1926: Max Mayer, a dealer in (Continued on page 33) 12 INTERNATIONAL PROJECTIONIST • October 1947