The Camera and its Accessories 5 
the plate, while the distance to the other edge is de- 
creased. This will have a tendency to sharpen the 
whole plate equally, producing a more uniform nega- 
tive in less time. . 
In purchasing a lens, there are several absolutely 
essential things to be considered—perfect definition, 
depth of focus, covering capacity, and speed. Begin- 
ner, beware of making the mistake of attempting to 
economize by using a small lens! Ifa 4X5 lens will 
make a certain picture in one second, with the dia- 
phragm at F 16, a 5X7 will do it better and in less 
time, for it is using the centre of the lens. J use on 
my F and S Graflex 4X5 a 7Xg lens. 
A long-focus lens is desirable for animal photog- 
raphy, because the greater the length of focus, the 
larger will be the image, and the less the distortion. 
For several years I have used a Goerz lens, series 
III, and for all-around work I have found nothing 
superior, although in some of the new series there 
are probably better lenses. My lens has an equiva- 
lent focus of ten and three-quarter inches; but by 
using the front lens alone, I have a focus of about 
seventeen inches. * This is of great importance to 
the field photographer; for with the shorter focus at 
the distance of sixty feet, an object twenty inches 
high forms an image half an inch in height; while 
