— 
s frame by | 
le 9, when 
an figure | 
10tographs 
but a com 
certain in 
18x18 | 
ik. infrared | 
| 
end 
8 fmm | 
m | 
95 | 
9u | I 
—— 
1/18 x If 
20.6 mm | 
184 > | 
Tp | 
— |l 
  
All resolution values stated in the above tables and curves are mean values 
a large number of negatives. It may, however, be of interest to know also 
from ; : : : 
imum values obtained in the evaluation; they are listed in table 11. 
the max 
537 Discussion of the results 
The investigations accounted for in the above tables and diagrams have pro- 
ceeded for four years. For this reason a comparison of the results during various 
vears for one and the same camera must be made, which shows that the values 
Jor the years 1952—1954 are in fair agreement with each other, whereas the 
photographs from 1955 and 1956 give higher line frequencies. The causes for this 
are more. Concerning the camera 15/23 x 23 the lens used in 1954 was substitu- 
ted for a new one in 1955. Also a new and more powerful illumination has 
been used for the evaluations of 1955 and later, and the old annular targets 
which were partly worn were replaced with new ones in 1955, the high-contrast 
line targets being replaced with low-contrast ones at the same time. For painting, 
a new paint was used that was somewhat less smooth than the former one. For 
comparisons stated above material has consequently been used that has been 
photographed on test targets of the same surface and evaluated under the same 
illumination. 
The effect of the flying altitude has been studied mainly for three different 
altitudes according to table 9. From 1,000 to 1,800 m the resolving limit increases 
by 22 per cent while the corresponding increase from 1,800 to 3,000 m is 14 per 
cent. It appears that the lack of definition due to motion has a greater effect than 
expected even at higher altitudes, whereas the deteriorating effect of haze is less 
noticeable. The latter can possibly be explained by the fact that all photographing 
had to be done relatively late in autumn when visibility was decidedly better 
than during normal photographing conditions in summer. 
Among the developers it appears that paraphenylenediamine and DK 20 give 
the best results. Since, among other things, the effect of the altitude has been 
noticeable, it has, however, been difficult to obtain a clear-cut comparison be- 
tween the results from the different developers. Kardas (8) has, however, shown 
in 1954 that the “information volume’ obtained with development in DK 20 
is larger than with development in, for instance, D 19. This applies to low test 
contrasts. In many cases, however, the exposure in the shadows is insufficient 
for fine-grain developers. For this reason DK 76 has, as a rule, been used with 
varying additions of Kodalk and bromide. 
With respect to the development time the highest resolving values are obtained 
as expected for very short times and low y-values (fig. 16). A development time 
of 2 to 3 minutes (DK 76) evidently gives the highest resolving limit. Prints 
from such negatives cannot, however, be used in actual practice where a develop- 
ment time of at least 10 minutes has to be used and the resolving limit drops 
Approx. 10 per cent. The results obtained are in good agreement with certain 
investigations previously made by Perrin and Altman (9), among others. 
49 
  
  
  
  
  
  
  
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