46 Photography for the Sportsman Naturalist 



be very careful that it fits perfectly tight, with no 

 possible chance for the admission of light. Also, 

 in screwing the lens into the flange, there is a 

 right and a wrong way, as one writer puts it. He 

 says : " The right way is first to turn the tube 

 backward i.e. the wrong way of the thread 

 until the two click at the point where the threads 

 meet. Then reverse the movement, and the lens 

 will enter its flange quite easily." 



If a lens sticks in its tube or flange, it is my 

 advice not to attempt to force it out by the use 

 of a vice or any other means, but take it to the 

 maker, who has the proper appliances and knows 

 how to do it, and who will not injure it as you 

 would be very likely to do. 



Finally, before buying a lens, first test it. 

 The dealers will generally allow this, and if you 

 do not understand how to do it yourself, you had 

 best ask some one to do it for you who is well 

 acquainted with the different lenses. 



Of shutters there is really little to be said, as 

 they are not complex and should be easily under- 

 stood by the average amateur. They can be 

 roughly divided into two classes : the diaphragm 

 shutter and the focal plane. The former is usu- 

 ally fitted between the two combinations of the 

 doublet or in front of a single lens and is made 

 to give, automatically, exposures ranging from 

 - of a second, in the best ones, to three min- 



