69 
6 9 
Figures 3 ànd 4 show Hakkarainen's results including phase 
changes, that is, positive and negative values, while Martin's 
and Rosenbruch's results are shown as modulation transfer values 
only, although a phase shift was recorded for the Pleogon lens for 
tangential bars at 35°. Also, with this one exception, Martin and 
Rosenbruch did not continue their measurements after reaching 
zero modulation transfer for the first time. 
Several general observations can be made: 
— The modulation transfer in the corner areas is higher in the 
Pleogon lens. In particular, very low values were obtained for 
the Super-Aviogon lens for radial bar targets; the low frequency 
phase change gives the impression of double images. 
- Hakkarainen's values for the Super-Aviogon lens deviate often 
significantly from those of the other contributors, indicating a 
sensitivity to focus. This sensitivity is also apparent from 
Martin's original values determined in planes parallel to and 
distant from the reseau plane by approximately 0, 25, 50, 75 and 
100 mm. Hakkarainen's values were determined in the image plane, 
parallel to the reseau plane and 160 mm distant from it. 
The areas within the image frame (113 mm by 113 mm for the RC8 
and 114 mm by 114 mm for the RMK) correspond to diagonal field 
angles of 46.1? and 46.7? respectively, the area within the reseau 
(110 mm by 110 mm) to a field angle of 45.7° for both cameras. Each 
contributor covered the field angle to a different extent:  Gliatti 
to 39? for the RC8 and to 30? for the RMK, Hakkarainen to 43? in 
the laboratory and to 34° for the RC8 and to 38° for the RMK in 
aerial photographs, Martin to 45°, Rosenbruch to 35° and Tayman to 
40°. Hence, information about the critical corner areas is somewhat 
sparse. 
3. IMAGE GEOMETRY 
The two cameras not only display significant differences in the 
lens quality parameters but also in image geometry. The average radial 
lens distortion as shown in Figure 5 has opposite sign for most of the 
format. In addition, the Pleogon lens available for the project has 
unusually large asymmetric radial and tangential distortion (Figure 7), 
while the Super-Aviogon (Figure 6) is almost free of such distortion.