International projectionist (July-Dec 1934)

December 1934 INTERNATIONAL PROJECTIONIST 23 IN THE EDITOR'S MAIL (Continued from page 12) more articles along this line in the I. P. Southwest Theatre Equipment Co. Wichita, Kansas. [To which need be said only that it all depends upon what is considered "acceptable" projection. Based upon projection standards of today, it is incredible that even the best 16 mm. projector equipment can deliver results comparable in any way with even passable 35 mm. carbon arc projection. There is a wide difference between good and bad projection work, of course, but in any discussion of projection or equipment it is assumed that we are aiming at the optimum. — Editor.] Single-Phase Rectifiers In "The Suprex Carbon Arc" article in your last issue you state that singlephase rectifiers are not satisfactory for the new Suprex carbon lamps. Does this statement imply that the two types (filtered and unfiltered outputs) both are unsuitable for single-phase work? May I suggest that a little information on this subject in an early issue would be greatly appreciated by many projectionists. Harold W. Wott Oak Harbor, Ohio. [This topic is discussed elsewhere in this issue by J. H. Elderkin under the title, "Single and Polyphase Rectifiers for Projection." — Editor.] TECHNICAL AND ECONOMIC ASPECTS OF SUPREX (Continued from page 11) is merely to make the mirror a little thicker. Mr. Brenkert : Is the guard made in the same mould as the mirror? The focal length of the reflector is an important factor, and it would, of course, be impossible to put the guard in exactly the same plane as that of the original reflector. Mr. Rubin: That does not matter; you simply focus the combination of mirror and guard. The fact is the Committee discovered that the focus was just as good with or without the guard. The loss of light was negligible ; we couldn't measure it. Committee Findings Correct Mr. Sachtleben : These reflections do occur, but most of the light so reflected adds to the light coming from the mirror. In view of the theory of application of the guard, the findings of the Projection Practice Committee are perfectly acceptable. Mr. Richardson : The Committee may have used a guard, the surface of which happened to fit exactly. There are about fifteen different mirrors on the market and they are not all made on one tool. Mr. Brenkert: Elliptical reflectors are not ground and polished. In other words, they vary in focal length as well as in working distance, or both. It may be possible to make a few sufficiently accurately to superimpose one upon the other, but in production in large quantities I am afraid trouble will result. If you want satisfactory The New BRENKERT rrrpr> High-Intensity Reflector Arc Lamp for D. C. Suprex Carbon Operation — is proving a revelation in screen results and low operating costs throughout the country • Wide range feed regulation with separate negative feed adjustment permits operating this lamp at 34 to 65 amperes with positive Suprex carbons of 6-mm., 7-mm., and 8-mm. diameter. • This is the widest range yet accomplished and permits a proper screen intensity to meet requirements of various size theatres with a range of operating costs to suit your pocketbook. • Rugged construction and accurate, dependable operation assures complete satisfaction. A Brenkert product throughout, which means a guarantee of perfect projection See the Brenkert distributor or write direct for literature to BRENKERT LIGHT PROJECTION CO. Engineers and Manufacturers 7348 St. Aubin Ave. Detroit, Mich.