CHRONOPHOTOGRAPHY ON MOVING PLATES 121 



the different parts acquire a uniform speed, but the 

 film remains stationary until the moment when the 

 observed phenomenon takes place. At this juncture 

 the operator presses the trigger, the film begins to 

 move, and the photographs are taken as long as the 

 pressure is maintained on the trigger; as soon as the 

 pressure is remitted the progress of the film is arrested. 

 The employment of this trigger makes it possible to 



Fig. 85 —Two successive photographs taken on a sensitized film. The image on the 

 left i* taken without arresting the onward movement of the film at the moment of 

 exposure; that on the right is taken with the film at rest. 



continue taking photographs until the bobbin is 

 exhausted. 



Shape and Size of the Photographs. — The shape and 

 size of the photographs should be in conformity with 

 the character of the subject, so as to utilize to the 

 best advantage the surface of the film. For this 

 purpose the opening of the admission shutter should 

 be regulated to meet the requirements of the case, and 

 the position of the apparatus correspondingly altered. 

 Thus the photograph of a man in an upright position 



