Fig. 3 shows measured distortion values of the lens. The curve proves that in 
accordance with the computed values the lens is practically free from distortion. 
The distribution of light of the objective at full aperture is illustrated by 
Fig. 4, which shows the path of illuminating power E in percentages of the value 
obtained in the image centre. It shows that the quality of the picture has not been 
obtained at the expense of an imperfect illumination of the margins. The distri- 
bution of light corresponds to the most favorable values which have so far been 
^4 
100 
80 
60 
40 
  
Et 
  
0 } } } + } 1 
0° Bildwinkel 10° 45° 20° 25° 30° 
Illuminating power E of Topar 1: 4/f — 210 mm at full aperture in 
percentages of the value in the image centre. 
achieved with well corrected objectives characterized by the same picture angle 
and ratio of aperture. As a result, no decrease of luminosity is evident on the 
photographs taken from the air. 
During the correction of chromatic errors allowance has been made for the 
fact that colour photographs will play a major role in the future. The objective 
may be used without hesitation without a yellow filter, provided that the trans- 
parency of the air permits taking colour photographs. 
AEROTOP([)