g shadows by 
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ictures contain, 
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en at once, or 
lose to doing 
  
following arc 
Ope. 
me to rewrite 
programme to 
ras, lenses and 
jr correct the 
h station near 
5 ft., about 2 ft. 
| "grey scale", 
matt paints of 
g the degrada- 
ided into 2034 
ssy black on a 
rovides both a 
shtness" back- 
  
Fig. 5 
The targets as seen from the ground 
  
  
  
Fig. 6 
A . . o . 
Enlargement of part of a negative taken from 1200 ft. with a 6in. lens. The length cf 
the ten-tone target was 160 ft. on the ground and 21 mm in the negative. (Scale of 
reproduction: 5.7 X original negative.) 
The first of these consists of 5 convex mirrors of various radii of curvature suitably 
mounted on the black box, which produce images of the sun ranging from 2.0 to 0.2 
mm. in diameter. These indicate the character of point source images and provide 
means of measuring image motion during exposure. 
For the second, 5 squares of plywood, 2 ft. X 2 ft., each with a square hole in the 
centre, 8 in. X 8 in., of various reflections from .90 to .04, mounted on the black box, 
a 
13