Journal of the Society of Motion Picture and Television Engineers (1950-1954)

camera utilized 70mm perforated film on 100-ft daylight-loading spools. It produces negative sizes of either 2\ in. by 5 in. or 2\ in. by 2\ in. It operates at variable sequence speeds up to twenty-five 5-in. pictures per second or up to fifty 2^-in. pictures per second. Its double rotating shutters, operating close to the focal plane, provide high motion arresting characteristics. The camera contains no reciprocating parts and since all moving parts are balanced and rotate at a constant preset speed, the camera has proven remarkably reliable and trouble-free. Rugged cast aluminum alloy construction and the absence of any small or intricate parts have proven more than equal to the abuses inherently associated with this type of installation. Description The exterior view shown in Fig. 1 indicates the general form of the camera. The lens mount slides in machined grooves in the front casting and may be removed to insert the desired lens. Focusing is accomplished by rotating the knob on the top of this housing which swings a front surface mirror into a 45° position reflecting the image onto the ground-glass screen for focusing. The 6-in. square base is designed to fit standard tripods. The camera weighs approximately 30 Ib. Figure 2 is an interior view of the camera's film transporting system. Film supply from spool D is fed over the sprocket and held in position by the film hold-down device G. It then passes in an easy loop over roller I through the pressure plate behind roller G, under the interrupter E and thence under the sprocket and on to the take-up spool. Both the sprocket and the interrupter rotate in a counterclockwise direction and at the same speed. Each revolution of the sprocket feeds 5T^ in. of film in on the topside and out on the bottom to the take-up spool. Except for the action of the interrupter, the film runs at a constant speed from the supply spool through the camera and on to the takeup spool. Rotation of the interrupter, however, changes the length of the film path between rollers G and F. This lengthening of the film path causes the loop above the pressure plate to be decreased when the film path below the pressure plate is extended, thus accelerating the film through the pressure plate. As the interrupter rotates, however, it leaves the film, causing an excessive loop to be formed below the pressure plate. While this loop is being consumed, there is no movement of the 5-in. strip of film held firmly by the constant force exerted on it by the pressure plate. The rotating-disk shutters are geared with the sprocket and interrupter in such a manner as to expose the film completely before it is again placed in motion. The doubleroller arrangement on the interrupter causes the film in the pressure plate to stop twice for each 5^ in. of film supplied by the sprocket. The shutters, however, are so arranged as to expose the film only once for each complete rotation of the sprocket and interrupter when taking 5-in. pictures. This shutter is replaced by another having double openings, and a mask is inserted in the aperture for taking 2j-in. pictures. In this manner the frame size is reduced from 5 in. to 2j in. in length and the camera produces pictures at twice the 5-in. frame rate while rotating at the same speed. The shutter system is composed of two 9^-in. diameter disks, Both of which rotate in the same direction. The shutter closest to the film plane serves to expose the film and is geared to make four complete revolutions for each 5^ in. of film fed by the sprocket. This provides a high traversing speed resulting in a short time increment between the top and the bottom of the 5-in. aperture. This exposing disk has one 21° opening. To prevent the film's being exposed four times, another C. A. Hulcher: 70mm Sequence Camera 249