926 



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 



