CAMERA EQUIPMENT 173 



will be the image of the " game " at a given distance 

 and the more objects will be in focus at the same time 

 at varying distances from the camera, both of which 

 matters are of great importance. On the other hand, 

 the longer the focus, or the farther away the lens is 

 from the plate, the less is the illumination and con- 

 sequent rapidity. But extreme rapidity is dearly pur- 

 chased for this work at the expense of depth of focus, 

 and it is better to be content with a medium rapidity, 

 which is quite ample. The doublet of a 4x5 size 

 should not be of shorter focus than six inches, and 

 that of the 5x7 at least seven and a half inches. 



A good plan, if one gets both types of cameras 

 and does not care to buy two lenses, is to secure an 

 anastigmat and use it interchangeably in both. The 

 lens-flanges on both cameras should be duplicates, and 

 the transfer can be made in a moment. 



There is another lens which is sometimes useful 

 in conjunction with the regular lens, the telephoto 

 attachment. This is screwed on to the doublet lens 

 and has a telescopic effect, increasing the size of the 

 image made by the doublet from six to eight diam- 

 eters, as desired. It must be fitted by the manufac- 

 turer or optical expert to the particular lens in hand. 

 It is an instrument of only occasional utility, and very 

 difficult to handle successfully. Directions as to its 

 use will be given in the next chapter. 



The general camera should be carried in a leather 

 case which is slung over the shoulders by straps. In 

 this carrying-case there should also be a compartment 



