AERIAL PHOTOGRAPHY. 
which ran paths mud-coloured like their surround ngs. Such success 
was achieved that in the photos. the paths stand out as white lines. In 
the manufacture of short-focus, wide-angle lenses, for the purpose of 
securing photographs over large areas in order to study massed torma- 
tion of troops, notable results have been achieved. The 4-in. Primo- 
plane lens, from an altitude of about 33 miles, has produced such sharp, 
clear images over the whole plate that in the enlargements barbed- 
wire entanglements could be readily detected. 
Tue Evonvurion or tHe Camera. 
Such wide-angle lenses will be of considerable value for aerial survey 
work over large areas, as a photograph taken on a 5 x 4 plate from a 
height of about 2 miles will cover an area of 5 or 6 square miles, and 
some of the automatic cameras in use can make 250 exposures of 
5 x 4in. pictures on a roll of film at one loading. In this way several 
hundreds of miles of country can be covered and photographed. Other 
cameras take large-size pictures (10 x 8 approximately) direct, and ean 
make forty exposures on a flight. 
THE TYPE “F” FILM CAMERA. 
The camera has gone through a rapid evolution. Many improve- 
ments were patented by Major Laws in 1917 in his B and F types of 
automatic cameras. Short-focus wide-angle lenses were designed for 
the low-altitude fliers, and long-focus lenses up to 30 inches for those 
compelled to fly high out of reach of the anti-aircraft guns. A series 
of cones were provided by which lenses of any focal length could be 
used as desired on the one camera. The shutter, being most liable to 
damage, was made of the self-capping roller-blind type, held in position 
by spring clips, and removable without interfering with the other 
mechanism. 
For general topographical survey work, a camera first used by the 
Flying Corps in 1916, and known as camera F, was exceptionally useful. 
\ continuous series of 5-in. x 4-in. pictures can be taken on a roll of 
film sufficient for 120 exposures. When the pilot wishes to take photos. 
he pulls a small lever. This releases the mechanism, which is operated 
automatically by a small air propeller, whose rate of revolution is 
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