20 WILD LIFE AND THE CAMERA 



use a convertible lens of 2 foci, it is advisable, for 

 though the single combination is slow it often 

 enables you to obtain satisfactory pictures of 

 animals entirely out of range for the ordinary 

 short focus lens. But don't lose sight of the fact 

 that the single combination means double the draw 

 of bellows required for the complete lens. It is 

 well to employ a lens, especially if it be a cheap 

 one, made to cover a plate one size larger than you 

 are using, so that there is no question of the entire 

 plate being clean cut. The ordinary lenses supplied 

 with cameras are usually too slow for animal work, 

 their aperture being as a rule about F. 8. How- 

 ever, they will do quite well under favourable 

 conditions, but don't forget that favourable con- 

 ditions are the exception rather than the rule, ex- 

 cept in such countries as Africa, or in the middle 

 western states of North America. It is nearly 

 always poor economy to buy cheap outfits. They 

 too frequently lead to disappointment, and when 

 you consider how much a trip costs, is it worth 

 while for the sake of saving a very small amount 

 to sacrifice the entire results, when by having a 

 good reliable outfit you may secure pictures which 

 will pay a part, if not all, of the expenses of your 

 outing? Should you wish to go in for telephoto 

 work remember that the positive lens should be of 

 very great rapidity, not less than F. 4.5, otherwise 

 the possibility of instantaneous exposure would be 

 limited to one or two magnifications. Never buy 

 the two elements separately, but let the manufac- 

 turer supply you with the complete lenses, positive 

 and negative elements properly adjusted. It is 



