International projectionist (Jan-Dec 1947)

INTERNATIONAL ROJECTIONISI With Which Is Combined Projection Engineering HENRY B. SELLWOOD, Editor Volume 22 JANUARY 1947 Number 1 Index and Monthly Chat 5 Magnetic Recording 7 H. E. Roys What Color-Correction Means . 10 Allen E. Murray Incandescent Lamps for Film Projection 14 J. J. A. Manders The New RCA Duo-Cone Loudspeaker 16 Presenting: Fred J. Loakes ... 17 The Trivision 3-Dimensional Process 17 In the Spotlight 18 Harry Sherman Elements of Projection Optics, V 20 Dr. Angelo Montani 25-30 Club Installs Officers, Confers Life Memberships 21 Letters to the Editor 22 Bi-Pack Photography Now a Formidable Color Entry ... 23 Trade Unions in America, II . . 24 Joe Robin 26 Personnel 31 I. A. Elections . 32 Unique Altec Speaker Display Uses 'Iron Lung' Principle . . 32 News Notes Technical Hints Miscellaneous Items Published Monthly by INTERNATIONAL PROJECTIONIST PUBLISHING CO., INC. 19 West 44 Street, New York 18, N. Y. R. A. ENTRACHT, Publisher SUBSCRIPTION REPRESENTATIVES AUSTRALIA: McGills, 183 Elizabeth St., Melbourne NEW ZEALAND: Te Aro Book Depot, Ltd., 64 Courtenay Place, Wellington ENGLAND and DOMINIONS: Wm. Dawson & Sons, Ltd., Macklin St., London, W. C. 2 Yearly Subscription: United States and possessions, $2.50 (two years, $4) ; Canada and foreign countries, $3; single copies, 30 cents. Changes of address should be submitted two weeks in advance of publication date to insure receipt of current issue. Entered as second-class matter February 8, 1932, at the Post Office at New York, N. Y., under the act of March 3, 1879. Entire contents copyrighted 1947 by International Projectionist Publishing Co., Inc. International Projf.ctionist is not responsible for personal opinions appearing in signed articles in its columns. 420 MONTHLY CHAT J2& b TESTIFYING to the extreme light-co: sciousness of projectionists is the raft of communications received following publication of the details anent the new National Carbon Co. experimental "Suprex" 9-mm/8-mm carbon trim which will burn at 90 amperes and 50 volts. We italicize the word "experimental" because this new trim still is just that, j., and we shouldn't like to have any of our'TY people go off the deep end and attempt to use this trim without the proper equipment therefor. National Carbon Co. is most emphatic on this point, its preliminary announcement thereon citing frankly the requisites for efficient operation of this trim. Not a few of the comments relative to this new trim reaching I. P. question the necessity for upping the amperage of the "Suprex" series in view of the existence of that old standby, the 13.6mm, 125-ampere, high-intensity carbon used with existing condenser-type lamps. It may surprise many projectionists to learn that the new 9-mm "Suprex" carbon, which will utilize a reflector mirror, will deliver as much, maybe more, of better quality light than does the 13.6mm, H. I. arc; and that its advantages are so pronounced in this direction that not even the necessity for utilizing some effective cooling means is considered a detriment. We doubt that the main problem here is the dissipation of the heat at the film aperture, important though this be. In several tests of the 9-mm trim, of which we have personal knowledge, it was the mirror that proved to be the weakest link in the chain. So intense is the heat radiated by this new 9-mm carbon that an ordinary mirror cracked in about 4 minutes time; and it is doubtful whether even a quartz reflector could stand the gaff. This indicates clearly that, in addition to cooling the film at the aperture, some means will have to be devised for cooling the mirror itself. One such means suggests itself: a continuous air blast directed at the back of the mirror. Just such a system was developed and patented some years ago by a projectionist in Ohio, whose name escapes us at the moment. We hope this item comes to his notice. Water-cooling of the arc itself is another alternative, although this method is at best cumbersome, requires auxiliary equipment which must give positive assurance of a continuous flow of water at a given pressure, and which might not be feasible in smaller theatres. Whatever the outcome of experiments now under way, it is evident that the projection process, far from being static, is the topic of much serious thought and extensive work by highly competent forces, whose work might well radically alter both projection equipment and technique in the next several years. As always, Mr. Projectionist must be ready. That decision is his to make. INTERNATIONAL PROJECTIONIST • January 1947