(34) 
Fig. 
11 Universal mount with cradle for film 
camera 
that the angle between the two surfaces 
is less than 1 centesimal minute (32 
seconds). IGN photography is done 
under the best conditions occurring in 
the time available. The poorest con 
dition usually encountered is tropical 
haze. Exposures are determined by the 
experience of the photographer. They range from f :6 • 2 to f : 14 with shutter 
speeds from 1/75 to 1/150 of a second. Usual altitudes above the terrain range 
from 3,125 m to 6,250 m (10,000 ft. to 20,000 ft.). There is no pressure, temp 
erature or humidity control. 
Photography by the Ministry of Reconstruction and Town Planning uses 
three gyroscopes to record the tilt of the camera. All three indicate the nadir 
point. Camera port glasses are not used. Some haze is permitted in photographs; 
the worst conditions under which photography is done is at an altitude of 750 m 
under cumulus cloud. Exposure is determined by means of a photo-electric cell. 
The normal exposure is 1/150 of a second at f :6 • 3. An auxiliary camera photo 
graphs the three gyros already mentioned. The most frequent operating alti 
tudes are 750 m, 2,500 m and 5,000 m (2,500 ft., 8,200 ft. and 16,400 ft.) above 
the ground. There is no control of temperature, pressure or humidity. 
Fig. 12 Panoramic mount for film camera 
Germany 
Camera mounts are supported on springs and rubber combined. Survey 
mounts have drift adjustment. A camera port glass is not considered serviceable 
for practical use. Exposure is determined by experience. Typical values are 
1/100 and 1/200 of a second at full aperture. Auxiliary cameras photograph a 
statoscope and two pictures of the horizon. Photographic altitudes are from 
800 m to 12,000 m. Image motion compensation devices under study involve 
displacement of the lens and an optical device with rotating prism. 
India 
A Williamson Mark V mount is used with rubber as the support material. 
A camera port glass is used in the Dakota but not in the DH Dominie. Photo 
graphy is done only in clear weather. One tenth scattered clouds (high strata)