220 
aD = D-1V 
At the linear portion of aerial film characteristic 
curve 
The above formula implies that Bg does not depend 
The aeronegatives also allow to determine the de 
pendence of water surface brightness on . 
Let us compare optical densities of sea surface 
images in the centre of the frame and at a point of in 
terest 
Bg 
Bg 
where ^ - Is contrast factor 
Using formula (3) we shall obtain 
iLl* 1 B °s 00 .ipcch-ti] 
1 h J 
(4) 
W-DtCtO'tflgC- 
Bg(j})- Cos 3 Ji 
Bg(o) 1 
ASC lens 
Multiplier Cos^Ji accounts for light weakening in 
Hence 
3/tgCosjJ/. 
(5) 
In this equation