16 BIRD STUDIES WITH A CAMERA 
son, we observe that the eight-inch gives a fairly 
wide field, excellent depth of focus, but a very small 
image of the bird, for which alone the picture has 
been made. With the fourteen-inch we decrease the 
4. Lens Test No. 2. Same subject, distance, plate, and date as Test No. 1. 
Front Jens (fourteen-inch focus) of Zeiss Convertible, No. 10; dia- 
phragm F. 16; ¥/s5 second. 
extent of the field nearly one half and almost double 
the size of the object pictured. This, however, has 
been done at the loss of depth of focus, not even the 
first of the line of posts running directly into the 
