International projectionist (Jan-Dec 1936)

July 1936 INTERNATIONAL PROJECTIONIST 23 possibilities as a wide-angle lens. A more detailed description of the German mirror telephoto lenses has been published, and there are the usual patents on new or improved forms of lenses. The Eastman Polo-Screen A very interesting accessory to the optical field is the Pola-Screen introduced by the Eastman Kodak Co. This screen gives the operator a hitherto impossible control of the polarized light entering the lens of the camera, making available several of its peculiar characteristics. The elimination of reflections is now simple, maximum results being attained when the optical axis of the lens is at a 32-degree angle from the reflecting surface, as at that angle the light reflected from most surfaces is fully polarized. Sky-filtering is possible when the lens axis is at right angles to the sun's rays, which will prove of value in color photography, since the PolaScreen is of neutral color value. The Pola-Screen opens up possibilities also in the field of stereoscopy, applying it in a manner somewhat similar to viewing a blue and red positive through corresponding blue and red glasses, but without the color interference. Stage Illumination. — The rapid progress made in new types of gaseous conductor lamps during the past year or so continues to be of outstanding interest in the lighting industry as a whole. The laboratories of the Philips Lamp Co. of Holland, as well as those of the General Electric Co. in the United States, have produced mercury-vapor lamps of the air-cooled type having brightnesses of the order of 20,000 candles per square-inch; and of the water-cooled type, about 150,000 candles per square-inch. By way of comparison, the old familiar Cooper-Hewitt mercuryvapor tube had a brightness of 15 candles per square-inch, and the highefficiency incandescent lamp can be operated at brightnesses up to 20,000 candles per square-inch. These lamps, in general, consist of a quartz tube with electrodes at each end, and are enclosed within a protective (housing. The experimental air-cooled lamps had light-sources approximately 4 millimeters in diameter and about 10 millimeters in length. The water-cooled types were slightly smaller. Since they possess the characteristics of an arc, they must be used in conjunction with either a resistor or reactance ballast. (Italics ours. — Ed., I. P.) Operating the mercury-vapor source at these high brightnesses results in considerable improvement in the quality of the light, but nevertheless the light retains much of its usual blue-green properties. At the present time their application as light-sources for studio motion picture photography appears rather remote, particularly when the severe requirements of color photography are considered. The extremely great brightness of the water-cooled lamp spotlights for both incandescent and artoffers possibilities as a projection source, lighting. Their 2000-watt Junior and Since photography is so dependent 5000-watt Senior Solar Spots, with Fresupon the source of light, mention should nel lenses, provide a uniform field of be made of the new Mole-Richardson illumination with no "ghost." This like A TREASURES /-/• M mepulauon By every standard, Strong Arc Lamps have attained a treasured reputation for being the reliable guide to better projection. See a demonstration in your own theatre. Any Independent Theatre Equipment Dealer will, without obligation, demonstrate the lamp meeting your requirements. Write today for the new, interesting and instructive catalog. THE STRONG ELECTRIC CORPORATION 2501 Lagrange Street TOLEDO, OHIO, U. S. A. Export Offices.: Room 301 220 W. 42nd St., New York City "INDEPENDENT"! ...and you patronize a LOCAL business! The "Independent" member in your territory is affiliated with a nation-wide organization of 43 theatre supply dealers. That affiliation helps him give you better service, better merchandise, better prices. At the same time he owns and operates his own establishment. He takes a personal interest in your problems, offers you the benefits of his broad experience. But above all, he is a local merchant who lives in and helps contribute to the welfare of the com munity which affords him a livelihood. His interests and yours are definitely intertwined ; to give him your patronage is to give it to the man who deserves it most ! §Vi INDEPENDENT •£us INDEPENDENT THEATRE SUPPLY DEALERS ASSOCIATION ROBIN, EXECUTIVE SECRETARY NEW YORK CITY