CAMERA EQUIPMENT 171 



and is the size preferred by most workers. Any- 

 thing less is too small. The 5x7 is better for scenic 

 pictures, but is unnecessarily cumbersome for work 

 in trees, as it is hard to screw up rigidly so heavy 

 an instrument. Furthermore, owing to the usual dif- 

 ficulty of getting very near any wild bird, one can 

 seldom secure an image of the subject large enough 

 to anywhere near fill even a 4x5 plate. A good 

 sharp image of a bird even half an inch long with 

 good detail can be successfully enlarged almost in- 

 definitely. I often secure, for framing, very clear 

 and good iixi4-inch enlargements from 4x5 nega- 

 tives. 



The reflecting camera, with Its ingenious mirror 

 arrangement for seeing the image of the game up to 

 the instant of exposure and its extremely rapid cur- 

 tain-shutter, is the only instrument adapted to secur- 

 ing pictures of birds in flight or motion, or by stalk- 

 ing. Further details of this will be found in another 

 chapter. 



As to the lens, it must be of the doublet type which 

 requires careful focusing. It should be of the largest 

 size and longest focus which will allow the use of the 

 single lenses of the doublet with the length of bellows 

 or ** draw " of the camera. The longer the focus 

 of the lens, the larger will be the image of a bird se- 

 cured at a given distance. Each single lens of a doub- 

 let gives about double the size of image of the bird, 

 from the same spot, as with the two in combination, 

 but the time of exposure has to be about four times 



