Apparatus for a Field Worker 93 



Of the telephoto lens I have already written, 

 and it needs only to be said here that it forms an 

 invaluable adjunct to the outfit. 



Among the shutters there is almost as great a 

 choice as among the lenses, but in buying one we 

 should be careful that, in making the exposure, it 

 works as smoothly and makes as little noise as 

 possible, for the click of a shutter is often suffi- 

 cient to scare a wary bird or animal. We must 

 also remember that, while each shutter has its 

 time-scale, these scales are seldom absolutely 

 correct, and that they are intended more to repre- 

 sent degrees of difference than exact measure- 

 ments of time. Thus, while most of the later 

 patterns of shutters are scaled to work automati- 

 cally at from about three seconds to the y^-Q- of a 

 second, they rarely exceed in speed T J-g- of a 

 second, and frequently the best they can do is 

 less than that. For extremely rapid work the 

 choice is not so great, however, but is limited to 

 one type : the focal plane shutter, which is capable 

 of making an exposure in T ^Vo ^ a second, but 

 which has been described elsewhere and so needs 

 no further mention here. 



For rapid work, also, such as birds flying, fish 

 leaping, animals running, etc., the only camera that 

 can be used successfully is one of the reflecting 

 type, which I have also fully described elsewhere, 

 or else a twin lens, which is more cumbersome, 



