CHRONOPHOTOGRAPHY ON MOVING PLATES 123 



executing movements on the same spot should be 

 taken on a surface the height of which is greater than 

 its breadth; on the other hand, two men occupied 

 in fencing would require an opening the breadth of 

 which is greater than the height (Fig. 86). The 

 same is the case in taking successive photographs of 

 a man rowing. The background of the image should 

 be regulated by reducing the opening of the admission 

 shutter to a greater or less degree. When the images 

 occupy most space in the horizontal direction the 

 camera should be turned over on its side ; the 

 successive attitudes should then be viewed by 

 beginning at the toj) and travelling downwards. 



Regulation of the Number and Size of the Images. — If 

 the progress of the film is uniform, and allows, say, 

 ten large images to be taken in the second, twenty 

 images half the size may, if necessary, be taken in 

 the same time, or thirty images a third of the size, 

 and so on. To effect this, the size of the admission 

 shutter must first be reduced to one-half or one-third 

 of its normal size. It is important that the circular 

 diaphragm should permit at the same time the 

 exposures to be twice or three times as numerous. 

 The fenestrations in the diaphragm should, therefore, 

 have curtains which can be drawn aside or closed as 

 required.* 



Reproduction, Enlargement, and Reduction of the 

 Photographs. — The size which we have selected for 

 chronophotographic images (9 x 9) is, as we said, 

 precisely that adopted for the plates used for enlarging- 

 cameras. Each photograph can be thrown on a screen, 

 if required for public demonstration. The strip of 



* In the arrangement we previously adopted, the number of times 

 the film was brought to a position of rest had to be regulated by 

 a very delicate manoeuvre ; this was dispensed with in the new 

 arrangement. 



