PHOTOGRAPHING BY ELECTRICITY 257 



which I know of is the " Anschutz " focal-plane. 

 I use this excellent shutter for slow exposures also, 

 owing to the silence of working. An interesting 

 point I have noticed in connection with focal-plane 

 shutters, is that when exposing with them one never 

 gets halation on the negative. Many of the birds 

 I photographed on the Fame Islands were against 

 the sky, and behind them was the strongest light ; 

 yet not a trace of halation is visible on the plates. 

 With the same exposure given with a shutter which 

 works on the lens, the birds would be almost invisible 

 owing to the halation, mostly caused by the reflection 

 of light from the inside of the camera. This is, I 

 think, one of the most important features in favour 

 of focal-plane shutters. 



The Cadett " Lightning " plates are the best for 

 rapid exposures, and I advise pyro-soda developer, 

 diluted with plenty of water for development. The 

 Cadett "Lightning" plates are, however, so exceed- 

 ingly fast, that care must be taken net to over- 

 expose. On a bright summer day an exposure of 

 i-6ooth of a second can be given when using Cadett 

 " Special Rapid " plates with a lens working at F 6. 

 The advantage of using the " Lightning " plates, 

 however, is that with a rapid lens it is possible to 

 stop down to F 1 1 and still give an exposure quick 

 enough for flying birds, and much better definition 

 is secured. If the best possible negatives are re- 

 R 



