These machines by no means exhaust the selection. Other manufacturers have produced very good instruments at competitive prices, but those which I have mentioned represent probably the best in their respective classes. For the purpose of introduction to the art of cinematography the beginner can do no better than obtain one of them. If, after a little experience, he comes to the conclusion that he has ventured into the wrong province, then his monetary expenditure is not serious.
It will be seen that the aspirant has no lack of inducement to embark upon the moving-picture industry. Provided he has acquired a certain knowledge of the elements of photography, and is possessed of average intelligence, there is no reason why he should not be able to produce pictures with his inexpensive machine that are in all ways comparable with the product of the professional worker and the costly instrument. Naturally, as the intricacies of the craft are mastered, the tyro will wish for a more elaborate apparatus. He can gratify his ambitions in accordance with his progress, or with the improvement in his financial position.
The mechanism of the modern cinematograph camera is very simple in its character and very easy to understand. The necessary parts are very few in number. In all cameras the chief object is to effect the forward intermittent movement of the film at regular intervals and for a defined distance. For this purpose the early types of camera were fitted with what is known as the Geneva stop movement. Opinion is divided upon its merits, some authorities condemning it unequivocally, while others uphold it strenuously, contending that it gives a steadier and freer motion. There is much to be said in favour of the latter view. Mechanically the Geneva stop movement is perfect. So far as cinematography is concerned its advantages were proved most emphatically by Mr. Robert Paul, the first man to bring motion pictures into commercial application in Great Britain. He adopted this movement in his camera, and it cannot be denied that his pictures were in every way equal to those produced to-day, while his camera has never been excelled. Curiously enough, although this movement has been superseded, there is a tendency among expert workers to revive it, and many cameras specially built have been fitted with it.
The movement more commonly used is that known as the "claw." It is simple, and has the advantage of bringing the film into place for an exposure with a sharp, quick jerk. But it is a movement which requires to be designed very finely in order to perform its work smoothly and evenly, and without inflicting any injury upon the film.
The claw consists of a small lever in duplicate, which is so mounted as to have an eccentric movement and is driven direct by the main gear wheel rotated by the handle. The free upper end of each arm of the lever has a projecting pointed tooth of sufficient size to engage with the perforations on either side of the film. With the revolution of the wheel upon which it is mounted eccentrically the claw engages with the perforations, and, thus gripping the film after the manner of a ratchet and pawl, jerks it downwards a definite distance. When this downward movement is completed the claw disengages from the perforations and falls back clear of the film. Then the wheel, continuing its rotary movement, proceeds to lift the claw. When it has raised it to its highest point it brings it forward smartly to re-engage with the perforations, and causes a fresh downward movement of the film. The action is intermittent and occurs at regular intervals, while the movement of the film is always the same. Quick engagement and disengagement of the perforations is imperative for preventing the vibration and tearing of the film.
Fig. 1.—Mechanism of camera showing threading of film.
The mechanism of the camera may be understood from the diagram ([Fig. 1]), which refers to the Williamson instrument. The sprocket A is driven directly by the operating handle, which engages with the sprocket spindle. This sprocket A is fitted with two rows of teeth, mounted upon its periphery, and so spaced apart, both circumferentially and transversely, as to coincide with the distances between the perforations of the film. A pair of twin rollers, D and E, bear against this sprocket under the tension of a spring, their object being to keep the film pressed firmly against the sprocket. The teeth engage with the film perforations, so that by the rotation of the handle and sprocket the film is fed forwards regularly, smoothly and evenly, as it is drawn from the loaded spool box B.