Practical Cinematography and Its Applications

by Frederick Arthur Ambrose Talbot

The camera may then be "threaded-up," or, if focussing is desired, this can be completed first. With the Williamson camera focussing is unnecessary within certain distances owing to the fixed foci of the stops. These will be explained later. Many other manufacturers of cameras follow the same principle, and it is most convenient for every-day work. Yet it may happen that the operator desires to focus critically. In this event he opens the side of the camera, lifts the pressure plate of the gate, and inserts into the gate window a small length, about 2 inches, of matt film, with the matt side towards the lens. The matt film serves exactly the same purpose as the ground-glass in the ordinary plate camera. The handle is revolved until the lens is opened, and the image thrown upon the matt film becomes apparent. This can then be focussed by moving the milled focussing screw on the lens until the picture stands out as sharply as is desired. At first the operation may appear to be somewhat awkward, because the operator has to look upon the matt film at an angle. It is easier in the case of a camera fitted with a focussing tube, for the operator has then merely to open the side of the machine to insert the matt film and push the telescopic tube out to its fullest extent to bear against the gate. By removing the cap from the tube upon the rear face of the camera, and looking through it as if through a telescope, he is able to look squarely upon his screen.

When focussing is complete the matt film is withdrawn and placed in a safe position. It is a good plan to clinch it to the bottom inner surface of the camera with drawing pins, for it can then be found when it is wanted. Should the piece be lost the defect can be repaired as follows. Take a small bit of waste film; scrape off the gelatine emulsion; and rough the celluloid surface with a piece of sandpaper; or even with a rough stone surface. It is well to carry a few inches of spoiled film in the pocket for such an emergency.

The film may now be threaded up. The loop of blank projecting from the dark box is picked up and the coil within is steadily unwound as the threading proceeds. The blank is first passed under the pressure roller (marked D in [Fig. 1]), and then under the spring roller E, which can be lifted for this purpose. It must be seen that the teeth of the sprocket engage with the perforations in the film. A loop G is then made and the film is threaded through the gate H. Before this can be done the claw N must be thrown in the "out" position to obtain access to the gate, which is done by turning round the eccentric. The spring part of the gate is then opened on its hinge, and the film is slipped in from the side. Care must be observed that an ample loop is left above the gate. When the gate is closed once more another loop I similar to that above the gate, is formed. The film now is passed round the under side of the sprocket A, the spring roller J being pressed back to admit of easy entrance, and the end of the blank is passed under the second or pressure roller K. Here again one must be careful to see that the insertion is square and that the sprocket teeth mesh with the film perforations. The film is then carried under guide roller L and through the velvet-faced slit into the empty film box C. This must be opened to permit the free end of the lead to be secured to the centre bobbin M, on which the film is wound in after exposure. The handle should be given a few turns to see that threading has been carried out properly, and also that it is properly attached to the bobbin M. If a sufficient length of blank is attached to the end of the unexposed film, and a piece of gummed paper is fixed on the lead about 6 inches in advance of the joint, it is possible to continue winding in on the lower bobbin until this mark appears at the mouth of the loaded dark box.

If the threading has been accomplished properly the interior of the camera should be as shown in the [illustration facing p. 42]. Here both film boxes are shown open, though of course the upper one is kept closed during the threading process. The most important part of this operation is the formation of ample loops both above and below the gate. Once formed they remain constant, because of the action of the teeth on the sprocket; for the movement of the ribbon over the sprocket is equal to that produced by the claws through the gate. At first sight the necessity of these loops may not be apparent, but when it is remembered that the film is moved through the gate intermittently, sixteen times per second, with a vicious jerk, it will be seen that if there were no loop, and the film were drawn directly from the dark box, a great strain would be imposed upon it, and probably it would break. But by providing the loop an elastic feed is secured, and the film is jerked into position before the lens with the minimum of vibration and without any risk of tearing or displacement.

Threading completed the lower dark box is closed and secured, together with the side of the camera, so that the whole of the interior is light-proof. The camera should not be re-opened after photographing has commenced until the whole of the film in the loaded box is exhausted, or, if the supply is not used, until the dark-room is regained, unless the waste of a foot or two of film is a secondary consideration. Should it become necessary to open the camera in the field, the handle should be given two or three turns to make sure that the last picture taken is wound into the exposed film box and is thus secure from the light. Opening the side of the camera obviously ruins the whole of the unexposed film threaded through the mechanism, so that when picture taking is resumed the handle must be given a few more turns to make sure that the whole of the light-ruined film has passed through the gate. Seeing that one turn of the handle represents eight exposures, equivalent to 6 inches of film, it is a simple matter to estimate how many turns of the handle are necessary to clear the gate of spoiled film.

Most cameras are provided with a film indicator enabling the operator to tell at a glance how many feet of film have been exposed. In this case, care must be taken to see that the indicator is returned to zero when the mechanism is threaded-up.

Another convenience is the "punch" whereby it is possible to mark the film after an incident has been photographed, so that the worker can afterwards tell in the dark room by a mere touch where the exposure ended in each case. The film should be marked after every episode is finished because it is then possible, if desired, to develop the film in lengths. Indeed it is advisable to follow this practice, and especially when the exposures have been made under varying conditions of light. By developing in sections one gets lengths of uniform density—a great assistance in printing.

The Williamson Camera threaded ready for Use.