12 BIRD STUDIES WITH A CAMERA 



greater speed of the two when combined, and fur- 

 thermore, because, being of the same focus, they 

 could, if occasion arose, be used in a twin-lens box. 

 The speed of the combination is registered at F. 6.3 ; 

 that of the single lenses at 12.5. With the former 

 the most rapid exposures can be made successfully, 

 while the latter are sufficiently fast to permit of 

 ordinary instantaneous work. This lens is stated 

 to cover a 5 X 8| plate, and when in use on a 4 X 5 

 camera gives a high degree of illumination and per- 

 fect definition. 



The telephoto lens may be employed in certain 

 kinds of bird photography with not unsatisfactory 

 results. Its disadvantages are lack of speed, an ex- 

 posure of at least one half a second to a second being 

 required at F. 8 in bright sunlight, the necessity 

 of extreme care in focusing, and of absolute rigidity 

 of the camera at the time of making the exposure. 

 In short, the telephotographer needs more time, 

 both before and after pressing his bulb, than the 

 bird photographer is often accorded. However, with 

 such subjects as nests high in trees or on cliffs, 

 Herons and other shore-inhabiting birds, Ducks on 

 the water or Hawks perched in leafless trees, the 

 telephoto will be found serviceable. 



Negatives are frequently secured in which the 

 figure of the bird, while small, is sharp, when, by 

 enlargement, a desirable picture can be made of 

 what in the original was too small to be easily dis- 

 tinguishable. An increase in size of two diameters 

 is possible from any fairly sharp negative, but if the 

 object be in perfect focus an increase of four diame- 

 ters may be made. 



