110 PHOTOGRAPHY FOR BIRD-LOVERS. 



much we decreased the exposure there would 

 always be a fraction of x left. Thus, since we 

 cannot really eliminate the " movement," the ques- 

 tion is how much can we permit for any given 

 purpose. And as a rough guide it may be said 

 that for contact printing and for observation with 

 the naked eye, a movement of about 1/1 00th part 

 of an inch is permissible. 



Although it is really more helpful to explain 

 the principles influencing the duration of high- 

 speed exposures than to attempt to give a table 

 of absolute speeds, yet I am so often pressed to 

 give the latter that I have drafted out a rough 

 suggestive outline of the uses of a few different 

 exposures, and hope they may at least afford the 

 beginner a starting-point from which to experi- 

 ment profitably and gain experience. 



A Suggestive Speed-Table. 



l/150th part of a second. This may be found 

 fast enough for work on flocks of Gulls, and other 

 birds of slow wing-beat, flying in the distance ; 

 for near studies of birds walking and otherwise 

 slowly moving, and for photographing stationary 

 objects when the operator is swinging on a rope. 



l/250th part of a second. At this speed one may 

 begin to attempt the portrayal of individual birds 

 in flight, so long only as they are flying either to- 



