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535 Aerial photography and evalution of test targets 
Je 
t targets were photographed in September and November 1954 and in 
September and October 1955. At this time of the year the solstice is lower than 
for aerial photography under normal conditions. The aircraft speeds varied from 
5) to 75 m/sec. and overlapping was approx. 80 per cent. Flying altitudes ranging 
from 1,000 m up to 5,100 m Were used. The number of flight strips is 149 and 
the test targets are generally found in 4 to 6 photographs per strip. A total of 
758 photographs with test targets were made. : : 
A preliminary attempt at testing camera vibration during photographing was 
nade in December 1955. The flying altitude ranged from 500 to 1,000 m and 
photographing was done at night with open shutter towards lamps that were 
lit and put out at certain intervals. 
High degrees of enlargement in evaluation have not resulted in higher resolving 
The tes 
values. A monocular magnifying glass with enlargement 8 x has thus been used. 
One single official has evaluated the whole of the new negative material. Random 
checks have shown good agreement with previous evaluations. 
€ 
596 Results 
A graph of the resolving limit drawn as a function of the distance of the test 
ligure from the centre of the photograph has been plotted for each flight strip. 
The shape of the mean curve for each of the camera lenses has been computed 
for each type of test figure by means of all available black and white photographic 
material. The contour resolution has in the same manner been stated in u. The 
distance of the mean curve from the abscissa has then been computed with 
guidance from the values obtained from the higher flying altitudes not affected 
by the lack of definition due to motion. The strips in which the resolving limit 
has been affected by less suitable development or exposure have not been used. 
The results from three modern cameras are to be found on fig. 13—15. 
The effect of the development time upon the resolving limit is shown in fig. 16, 
while the resolving limit for dark targets as compared with bright targets at 
different times of development is shown in fig. 17, where the value for the bright 
  
Table 9. Variation of resolving limit according 1o altitude 
  
Increase from Increase from 
[ype of test target 1,000 m to 1,800 m| 1,800 m to 3,000 m 
  
  
  
  
  
  
es dark, lee (La) =D % 12 % 
hm eere v lon <a) 18 % 10 % 
Annuler dark, ................. (Aa) 18 % 26 % 
fionlatbrightd, 0. .............. (Ap) 18 % 20 % 
amularecolourts; Lu ............... (Ac) 30 % 5 5 
Contourshigh-contrast’. . . . .. (Ch) 12 % 14 % 
T—561100 45 
  
  
  
  
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