International projectionist (Oct 1931-Sept 1933)

Urreinhcr 1931 INTERNATIONAL PROJECTIONIST 31 S275 a pair WEBER SYNCROFILM SOUND EQUIPMENTS HAVE STOOD THE TEST IN AMERICA'S FINEST THEATRES not a bit EXPENSIVE yet such QUALITY! SYNCROFILM "B" SOUND HEAD For Simplex or Powers Compact and sturdy in construction, simple to operate, perfect in efficiency. Smooth, quiet, positive drive assures even tone quality without distortion. Sound heads are furnished complete and include optical systems, photo-cells, exciter lamps, adjustable motor mounting brackets, endless woven belts, grooved motor pulleys and all necessary attachments for projector. Money-Back Guarantee Easy to Install WEBER MACHINE CORP. 59 RUTTER STREET ROCHESTER, N. Y. Export Office: 15 Laight St., N. Y. C. A MODEL FORM OF PROPAGANDA FOR PROJECTIONIST UNIONS George A. Yager BUSINESS MANAGER, SALT LAKE CITY L. U. 250 TO begin any clear explanation of motion pictures it is well that you should understand that motion pictures are not really motion pictures at all, but a series of still photographs projected upon a suitable surface known as a motion picture screen. These still photographs, the approximate dimensions of which are % by % of an inch, are projected onto the screen at the rate of 16 or more per second. The sensation of motion in these pictures is made possible by two f acts :. first, the rapidity with which they succeed each other upon the screen, and second, the persistency of vision. Persistency of vision is that quality of human sight through which the vision of an object is retained by the eye for an instant after the object is removed from sight. Due to this quality it is not only possible but a fact that 16 times every second the motion picture screen is in total darkness, that is, there is no pic ture being projected upon it. This period of darkness is caused by the interruption of the light rays from the projector by what is known as a shutter and which resembles, in appearance, the wheels which are used on the parade wagons of a circus, in that they have alternate spaces of solid material and spaces which are punched out. Light Sources In the early day of the motion picture industry one of the greatest difficulties that had to be overcome was the perfecting of a suitable light source with which to illuminate the screen. An ordinary light would not do for the reason that the source itself has to be of very small dimensions; and in the beginning of the present century the only known method of obtaining a light of any intensity was the electric arc which at that time was available only in a very crude form. The carbons which are used in an arc lamp to burn steadily and without flutter or flicker must be of uniform density throughout. Carbons themselves are made through a manufacturing process by which carbon, lamp-black and water glass, or silica, are combined. The lamp black and silica are used merely to hold the particles of carbon together. In some of our modern carbons there is a special inner core which is treated with various chemicals in order to improve the quality and quantity of light. Other forms of modern carbon are coated with copper in order to reduce their size and at the same time make them burn at the same rate as the larger uncoated carbon, which works with them. The reduction of size of the copper-coated carbon is for the purpose of increasing the amount of light from the other carbon by reducing the size of the shadow cast by the copper-coated one. Dr. Sapington of the National Safety Council advises me that lead has been discovered as an impurity in the coppercoating of carbons and that lead poisoning is a possible vocational hazard of projectionists. In the early days of the industry 30 amperes current was about the maximum amount used on a carbon arc. However, with the passage of time