Exhibitors Herald (1927)

October 1, 1927 EXHIBITORS HERALD 51 quickly and effectively remedied. That the trouble be remedied as soon as possible is imperative. * * * AUTOMATIC SILVER RECOVERY FROM HYPO By K. Hickman and D. Hyndman In the basement of every film laboratory there is to be found a large tank for treating waste hypo. Of the many methods of treatment adequately described by Crabtree, those using zinc dust or sodium sulphide are the most popular. The hypo solution is permitted to accumulate until the tank is full, reagents are added, and the desilvered hypo allowed to flow to waste after settling overnight. The scheme described in the present paper uses the conventional sodium sulphide method but performs the operation continuously and automatically. Waste hypo is allowed to drop into a measuring vessel fitted with an automatic syphon which flushes at a predetermined head. During the flushing operation waste developer and sodium sulphide are sucked in and the mixture discharged into a reaction vessel. From here the solution and precipitate trickle slowly down a funnel to a settling tank. The precipitate collects as a thick brown sludge below the funnel and is drawn off into a bucket with a perforated bottom covered with absorbent cotton. The clear, desilvered hypo flows to waste from the top. This process makes possible the saving of considerable money, in the past often lost down the sewer or in inefficient and time-wasting processes by which silver was recovered. * * * IMPROVEMENTS IN MOTION PICTURE LABORATORY APPARATUS By R. C. Hubbard More and more specialized machinery is being used each year in producing motion picture film of good uniform quality and at a considerable saving in labor. It is expected in the near future that the negative film will be taken directly from the cameraman and by a continuous series of operations in a single machine will pass through the developing, fixing, washing and drying operations to be taken out of the machine wound up ready to have prints made from it for the screen. Other mechanical aids in motion picture film laboratories include a device by which a loop of motion picture film 1,000 feet long can be used on a printing machine, a great saving in time being effected and the risk of damaging valuable films lessened ; mechanical means for quick, accurate examination of film lead to improved pictures and greater economy. * * * FACTORS AFFECTING THE CONTRAST OF A LENS IMAGE IN THE MOTION PICTURE CAMERA By Clifton Tuttle and H. E. White An image which duplicates the contrast of the object is desirable in photography. Such a condition makes for a clear, sparkling picture, but if the lens image contrast differs greatly from that of the object, the quality of the photographic reproduction will suffer. In motion picture photography a number of causes such as lens flare, camera interior reflections, diffusion and light leaks may result in lowered image contrast. The seriousness of these various factors and the possible remedies for some of them are discussed. Especial attention is given to the practical value of lens shades in preventing the entrance of extraneous light. ( Continued on page S3) (Eighteen Years of— PIONEERING FOR each type of auditorium and light source there is a special type of DaLite Screen backed by our unconditional guarantee of satisfaction. SINCE the initial demand for motion picture screen, Da-Lite has been a full step in the lead. Many of the most important advances — even to the perfection of screen frames — have been Da-Lite in origin. The introduction of Tear-Proof Fabric ten years ago made the screen practically a permanent unit of theatre equipment. The majority of screen manufacturers today, advertise heavy fabric screen but the original Tear-Proof is an exclusive Da-Lite feature. And through these eighteen years of pioneering, Da-Lite still leads with the only genuine Tear-Proof Fabric Screen — seamless in any size. DA-LITE SCREEN CO. CHICAGO CHOICE OF THEATRES For Perfect Curtain Movements Perfect Showmanship and Performance are created with the A.D.C. Curtain Control of unusual quiet operation. It is controlled from any point of the house by “simply pressing a button.” For Best Screen Results Every part of this Stabilarc represents the best of materials and workmanship. Manufactured in Series and Multiple types and in all commercial voltages, cycles, phases and sizes. AUTOMATIC DEVICES CO. 737 HAMILTON ST. ALLENTOWN, PA. WRITE FOR OUR NEW LITERATURE