The international photographer (Feb-Dec 1929)

June, 1929 the INTERNATIONAL PHOTOGRAPHER Twenty-one In position 3, the film feeding fingers have reached the end of their upward stroke and are advancing into the perforations. The registration fingers are still engaged. In position 4, the film feeding fingers have moved forward slightly and the registration fingers are withdrawing. This phase of the movement is difficult to illustrate in proper proportions since it involves the simultaneous motion of feeding and registration fingers which covers distances but a few thousandths of an inch long. In position 5, the film feeding fingers are carrying the film downard and the registration fingers are in their retracted position. The IN and OUT movement of the fingers is accomplished by means of two adjoining cams which are integral parts of the crank shaft. These cams provide positive forward and backward movement to the fingers and eliminate the use of springs. No damage can possibly result from undue friction or strain upon the film perforations. The motion producing surfaces of each cam subtend an angle of 12 degrees which is but 1-30 of its periphery. There is no load upon the inactive parts of the cams. The cam's rollers are freely fitted in their sockets; they creep around very slowly while in contact with the active zone of the cam and each point of their surface incurs an equal amount of wear. They can easily be removed and replaced in their sockets without the use of tools, should the inevitable wear produce any loose motion. The lubrication of the cams and rollers is assured by oil saturated felts which are in constant contact with the periphery of the cams. The exposure condition is met by this new mechanism as in the usual 170 degree shutter cameras. THE REGISTRATION FINGERS:— In order to insure the perfect registration of each photographic image on the film and to insure that there will be no motion in the film during the time of exposure, two pairs of registration fingers have been provided in this mechanism. These fingers engage the perforations at the end of the film feeding stroke, become stationary when fully engaged and remain so until the beginning of the following stroke. The manner in which these fingers sieze the film, is entirely new. At the moment at which they have fully completed their forward movement, they become wedged against the faces of the film pei-forations by spring pressure. The film itself serves as a stop for the fingers, and the spring pressure locks both fingers and film, assuring absolute rigidity and perfect registration. The registration fingers are also chromium plated in order to insure their longest possible life. PIVOTS AND BEARINGS:— There are only three points in the mechanism where bearings are used. The pivot bearings are adjustable and very generously calculated so that the perfect functioning of the movement is assured throughout its life. LUBRICATION; — The cams and rollers are lubricated as previously explained by felt wicks and the same system is used for the constant lubrication of the other rapidly moving surfaces. Oil holes are provided for the proper lubrication of the other parts of the mechanism. GENERALITIES: — The movement proper is built around a single piece of hardened steel. All holes which are to receive pivots and bearings are bored after hardening, with tolerances of .0001 inch. The movement is entirely enclosed in an aluminum cap which serves the threefold purpose of rendering the mechanism light-proof, of preventing the spattering of the lubricating material within the camera and on the film when the movement is working at full speed, and as a protection against dirt from outside sources. Provisions have been made for the mounting of a total reflection prism in the aluminum cap of the mechanism, so that a direct focusing magnifying optical system can be mounted on the camera. The installation of this new mechanism in the Bell & Howell camera is extremely simple and requires, as the old movement, only to be slipped in the proper position and fastened there by two clamps. No alterations of the camera are necessary except for the main cam, in which a worm has to be mounted to drive the mechanism itself and for a hole to be bored in the inner frame of the camera in order to provide space for a gear which is driven by the worm. The whole mechanism which, as it has been seen, is built upon very simple lines, is remarkably small in size and presents at the same time all the necessary requisites of remarkable sturdiness and endurance. An extremely careful adjustment of all its parts insures a most perfect functioning as well as a total absence of the noises which are so detrimental to the making of sound and talking pictures. Fig. 1 Fig. Fig. Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 ILLUSTRATIONS Belt-tension equalizing attachment for camera magazines. 1000 foot Silenced Film Magazine. Two views of the B. & H. motion pictures camera equipped for sound work. Silenced B. & H check pawl super speed intermittent mechanism. Schematic drawing of the new B. & H. high speed intermittent movement mechanism. Film tension in the new B. & H. high speed intermittent movement mechanism. Comparative curves of the acceleration by a constant force with the acceleration obtained through the movement. Schematic drawings illustrating different phases of the cycle of movements performed by the new B. & H. high speed intermittent movement mechanism. Handling Sound Film (Continued from Page 3) which take place during projection. All of these faults cannot be blamed upon the operation of the equipment as heretofore has taken place. We have noticed lately that sound prints which are synchronized with discs have been coming through with very poor photography, and upon looking into the matter find that incandescent lighting is being used on sound features in preference to arc lighting. In our opinion arc lighting is far superior to the incandescent lighting for sound pictures. Many theatres have suffered because of the poor photography and patrons do criticize a production severely when they cannot clearly see the object on the screen. Most theatres are equipped with the best possible equipment with which to illuminate the screen properly. It is impossible to shoot through film which is very dark and obtain good results. We have advised and instructed every projectionist in our theatres to handle sound film with great care and, upon checking into this matter, we find that the sound prints last just as long as silent prints. There have been many discussions about the life of sound prints. We might say that the print "IN OLD ARIZONA," which opened at the Fox Criterion Theatre, is still in use and the reason of this was the proper handling of this film. The projectors must be kept in good condition at all times and proper tension must be applied against the film at the aperture, keeping in mind that excessive tension is one of the many things which ruins film as the sprocket perforations will not stand excessive strain. Many theatres have been criticized severely because of buckling which causes an in-and-out-of-focus effect on the screen, and this suggests one of the things which, we believe, should be watched by the laboratories. It is that film should not be stretched tightly when placed upon the drying drum, as it has a tendency to stretch, and this has caused considerable buckling.