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The graphical data in Fig. 1 must therefore be evaluated with this reservation. 
‘The test objects were radial and tangential grids which were exposed on the pan- 
chromatic Perulith plate by Perutz, which is frequently used for tests, and on a 
highly sensitive emulsion for aerial photographs, namely the Aviphot Pan plate 
  
— 40 U | 
0 ———— ea 
Bildwinkel 10° 15° 20° o . 
+40 u 25 30 
Fig. 2 
Distortion of Topar 1:4/f = 210 mm in 1/1000 mm = 1% 
30? Sch. by Gevaert. In the former case, the development was made with the 
Perutz fine-grain compensating developer for a period of 6 minutes, and in the 
latter case in Final with a developing time of 10 minutes at a temperature of 
20? C. The grids showed the logarithmic contrasts K — 1.6 and K = 0.25 which 
were measured by us photoelectrically. The lighting was supplied by a nitra lamp. 
The exposures on the Perulith plate were made without filter, whereas the expo- 
sures on the Aviphot plate were made with the yellow filter D (Schott glass 
OG 1). 
The figures given in Fig. 1 represent the number of dark lines resolved per 
mm. They apply to the objective with the focal length f = 210 mm at full aper- 
ture. If a shorter focal length were used, these figures would be improved, whereas 
a longer focal length would give less favourable results. The definition in the centre 
extends to an extraordinarily large range and remains practically undiminished 
over a distance of the length of the picture size. Aerial photographs confirmed 
this uniformly sharp definition of the commonly used image field and showed 
that the slight deterioration of definition toward the corner of the image has no 
importance. 
The distortion of the objective, that is the displacements of the image points 
with reference to the correct location they would have if no distortion were pre- 
  
— 10 | 
+10 p | Bildwinkel 40° 45? 20? 25° 30° 
Fig. 3 
Distortion of Topar 1:4/f= 210 mm in 1/1000 mm = 1 u (measured values). 
sent, is illustrated in Fig. 2. The displacements are less than + 3 #. 
The curve in Fig. 2 is the exact result of the optical computation, which also 
showed that the values are not affected by the diaphragm settings of the objective. 
However, we wish to point out in this connection that we would not use a dia- 
phragm with a high-grade objective of this type; it may be advisable to use the 
illuminating power of the objective for a reductionof the image movement (blur). 
19