40 BIRDS 



The cheap meniscus F. 16. 



Single Achromatic F. 11. 



Rapid Rectilinear F. 8. 



Anastigmat F. 4. 



Thus the F. 4 lens works at about four times the 

 speed of the F. 8. In other words, if an exposure with 

 an^ anastigmat lens working at F. 4 required one second, 

 using the rapid rectilinear would require four seconds, 

 at its largest working aperture, or F. 8. 



The rapid rectilinear lens consists of two single ele- 

 ments, which may be used separately with about double 

 the focal length and size of the image. This type of lens 

 requires a smaller diaphragm opening than the anastig- 

 mat to secure sharp definition in the negative, hence is a 

 much slower lens than the anastigmat. The latter lens 

 is a more expensive one. 



While the anastigmat lens is fully corrected and is 

 nearly as perfect as a lens can be made, under some light 

 conditions and extensions of bellows it occasionally de- 

 velops a flare spot, and either destroys the negative or 

 reduces its brilliancy. All shining metal surfaces within 

 the camera and shutter should be given a coat of black 

 finish. 



The cheap fixed focus cameras, while giving great 

 depth of field, have uncorrected lenses and should not be 

 used for this work. 



If you are going to make pictures of birds worth 

 while you must expect to devote much time and have un- 

 limited patience ; added to these must be a practical work- 

 ing knowledge of how to use a first-class photographic 

 equipment. My equipment consists of three cameras, a 

 number of the best anastigmat lenses and a telephoto lens 

 with about a nine magnification, as compared to an ordi- 

 nary 6-inch focus lens. All the cameras are equipped 

 with a ground glass for accurate focusing and a good firm 

 wooden tripod, to which is fixed a tilling tripod head for 

 use in picturing on the ground and in trees. 



One of my cameras is a Gundlac 4x5 revolving back 

 plate-using machine, fitted with a front and back exten- 

 sion of 22 inches. This long bellows is used in connection 

 with the telephoto lens. To this camera I have fitted a 

 number of lens boards. The lens I use for ground, tent 



