606 BIRD PHOTOGRAPHY 



remembered that although an aperture of /6, or even/4'5 if it can be afforded, may be more or 

 less of a luxurious reserve, yet when it is wanted, it is wanted very badly. 



Most, but not all, modern anastigmat lenses are convertible, i.e. the front or back combina- 

 tions can be used separately. Either combination used by itself has a considerably longer focus 

 than the complete lens. The ratio varies in different makes; but as an average one combina- 

 tion of an 8" lens may be 12" and the other 14". so that in one lens there may be a choice of 

 three focal lengths. The value of this is obvious, as although a single combination is not so 

 rapid as the complete lens owing to the fact that not only is the / value of the lens reduced by 

 the increase of focal length, but with most convertible lenses to obtain a sharp focus with a 

 single combination a moderately small stop must be used ; yet when for some reason the 

 camera has to be placed farther than usual from a nest, the size of image need not be reduced 

 if light and other conditions allow of sufficient exposure being given to suit the requirements of 

 the single combination. 



The two photographs (Figs. 3 and 4, Plate LXXIX.) show clearly the gain in size of image 

 by the use of a single combination of the lens. While the result is similar to that attained by 

 the use of a telephoto lens, the working differs in this important particular a telephoto lens 

 magnifies, and therefore requires but a short camera extension, while the long focus lens, 

 especially when used on a near object, requires a very long extension. Hence the importance 

 of choosing a camera with the longest extension possible. I frequently require the full 23" 

 extension of my 5x4 camera. 



SHUTTERS. For short exposures from -fa of a second down, a focal-plane shutter is best, 

 while it is the only form with which the extremely brief exposures necessary for flying birds 

 can be obtained. In addition, it is more efficient at a given exposure than a shutter working 

 on or near the lens. 



For prolonged exposures I have so far found none better than the Thornton-Pickard 

 " Silent-Studio Shutter." This shutter should be fitted behind the lens. It has double roller- 

 blinds lapping in the middle, which open on squeezing a rubber ball and close on its release. 

 With it, it is possible to give exposures from | of a second to any required length. The " bulb " 

 action of a between-lens shutter will, of course, do the same, but the opening of these shutters 

 is accompanied with a click that is apt to startle the bird. 



To sum up, the outfit recommended above should comprise the following : 



Tripod. Strong, telescopic if possible ; with a range of elevation from 6 feet down to 

 2 feet. 



Tilting-table. 



Camera. 5 x 4, triple-extension, racking both ways ; reversing and swing back. 



Lens. Convertible; focal length 8"; aperture not less than/6. 



Shutters. Focal-plane (the quietest procurable) fitted on back of camera ; Silent-Studio 

 or similar make behind lens. 



Plate-holders. Plenty of any kind that will carry the plate securely and are simple to 

 manipulate. 



Small pocket-mirror ; string; pins. 



Although in most bird-work the camera must be used on a stand, yet there are occasions 

 when a hand -camera is not only useful but necessary. The best form is the Reflex, as with it 

 the image can be seen on the focusing screen and the focus adjusted up to the moment of 

 exposure. It is especially suitable for photographing flying birds. There are many good 

 Reflex cameras on the market, but one, called " The Birdland Camera," is made specially for 

 bird-photography. It is very strong- has extra long extension, and can be used equally well 

 as a hand or stand camera. It is fitted with an admirable focal-plane shutter probably the 

 quietest made. The lens usually supplied is a Goerz anastigmat, and although any other lens 



