DESCRIPTION OF THE APPARATUS 



other conditions, the use of objectives of short focal 

 length is less convenient. 



If the object to be photographed has any depth, it 

 will appear at different points of its course in different 

 perspectives, that is to say, when the observer is only a 

 short distance off. But this difference in perspective 



Fig. 54.— Chancres which occur in the perspective oT a moving ar.imnl ac orJing to 

 the distance off at which the photographic apparatus is placed. 



becomes less as the observer moves further away from 

 the object. To take an example : Suppose a bird flies 

 in front of a camera, and that we observe its positions, 

 when it is to the left of the camera, when it is exactly 

 opposite, and when it is to right (Fig. 54). In the 

 first case the bird will be seen from the front, in the 



