Principles of cinematography : a handbook of motion picture technology (1953)

THE CINEMATOGRAPH CAMERA 49 number of machines were made by the Biograph Company. One of the machines used by this concern is shown in Figure 13 and is seen to consist essentially of two mutilated rollers. These rollers are so positioned that, when in mesh, as seen at 'B', the film will be gripped and caused to move downwards. When in position 'A' the film will remain stationary and the exposure may be made. Such a condition will only exist if a heavy tension is provided between the members forming the gate channel. When such a mechanism was used in a projector it suffered from similar disadvantages as were encountered with the dog movement. To overcome loss of 'framing', that is, in an attempt to hold the picture steady when the film pitch varied, provision was made whereby one roller could be advanced with respect to the other. This condition is seen at 'C and 'D', Figure 13. Such an adjustment served to reduce the total time during which the rollers were in engagement with the film and, consequently, reduced the amount by which the film was advanced during one revolution. Quite apart from the aforementioned disadvantages, the mechanism was liable to lock solidly if an attempt were made to pass joined film through the rollers since, under such conditions, two thicknesses of film were required to pass between them. It is not surprising that, at this stage steady pictures were the exception rather than the rule and the cinema became known as the 'jumpers'. Although many different intermittents were devised in an effort to improve this condition, all have been rejected in favour of the claw mechanism some form of which is now used in all cinematograph cameras. © D £<0 Fig. 13.— Intermittent film motion by mutilated rollers.