Page:Popular Science Monthly Volume 90.djvu/942

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��Popular Science Monthly

��leaves can be altered, while maintaining a perfect rectangle. The square closing dis- solver and the vignetting shutter are gener- ally mounted in the same barrel so that either one may be used at will. In the case of the former device, it is placed as far away from the camera lens as is possible, so as to obtain sharp edges on the film images.

Still another device, the "curtain dis- solver," is similar to the two devices just mentioned. Its effect is to cause the top and bottom of the film image, or the sides, to move toward each other. If desired, only one side of the picture is moved so as to stimulate the pulling down of a curtain or the drawing of a screen, or rolling door across the film image. It is employed to secure a narrow picture or to isolate a single narrow object, such as a doorway or perhaps a railroad switch. The device em- ployed consists of two shutter blades which may be moved toward each other or moved singly, by means of levers.

Sometimes the "curtain dissolve" is em- ployed in double exposure work, in which case its blades are used to mask certain sec- tions of the film during the different ex- posures. One blade is first moved up to a definite point so as to reserve a certain amount of space on each film square, while the first action is photographed. Here, too, the cameraman must keep track of the number of feet ©f film that are exposed, and, masking the lens, wind the film back to the starting point. The other blade of the dissolver is then moved over to meet the first blade which is then moved out of the way of the lens. Great care must be taken that the action of the second exposure coincides precisely with that of the first, for otherwise the effect fails to be convinc- ing and may even be ludicrous. This effect makes it possible for an actor to play op- posite himself. Entire film stories have been built around the cameraman's skill in this form of double exposure work. In good work the two sections of the picture are so carefully matched that they blend together with no dividing line showing.

Another method of double exposure work makes use of what is known as the "double exposure box." This device comprises a simple box placed in front of the camera and carrying a piece of ordinary glass, through which the camera photographs the scene. In taking the first action, any por- tion of the film may be masked out by pasting opaque pieces of paper of any size

��and shape on the glass window of the box. The film is then wound back to the starting point, with the lens masked in the mean- time. The second action is then taken, after the glass window has been altered so that the portion formerly covered is un- covered, and the former transparent por- tion is covered. The result is that two dis- similar actions can take place in the same film scene.

This form of double exposure, it will be noted, confines the different actions to separate sections of the film. It is some- times termed "split stage" double exposure. There is still another form of double ex- posure work where the two exposures are photographed on the entire film or are superimposed in part, such as the cloud effect, shown in one of the accompanying film strips. This effect is either obtained in the photographing, or in the double printing of the positive stock, with many interesting and weird results. Sometimes the titles of a film are printed in on the scenes, or the dialogue is printed in some convenient portion of a scene, which is accomplished in the printing process.

��Dropper Bottle for Photographic Bromide Solution

A TEN per cent solution of potassium bromide is kept on hand in almost every photographic darkroom. The usual developing formula calls for a certain num- ber of drops of the bromide so- lution. A handy dropper for this can be made by fitting a small large -mouthed bottle with a two-holed rub- ber cork and inserting a short piece of straight glass tubing in, to one of the holes, while in the other a curv- ed tube is inserted, its upper portion tapering like that of an eye-dropper. This tube extends to the bottom of the bottle. At the top of the short tube a rubber bulb is attached. When the cork is tightly fitted and the bulb squeezed slightly, the bromide solution in the bottle will flow from the tapered tube in drops..

���Drops of bromide solution forced out by pressure

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