contact surface 
A 
N 
The arrangement for cooling the camera lens 
Fig. 10 The arrangement for cooling the camera lens. 
old camera Williamson Eagle III with the lens Ross Xpress, c — 126 
mm and the image format 12 X 12 cm. The most suitable arrangement 
was found to be as follows, see Fig. 10. 
A circular container of aluminium was mounted around the front 
of the camera. In the container alcohol and carbonic-acid snow were 
mixed, which gives a temperature of about — 65? C. The low tempera- 
ture of the aluminium container was then transferred to the camera via 
the contact surface on the lens cone. In order to keep the front lens free 
from condensation compressed cold air was blown over the lens from a 
pneumatic container. For the measurements of the temperature in va- 
rious parts of the camera thermoelements of cupper-constantan were 
used which were connected to an automatic electronic potentiometer. In 
this way a very effective temperature control was arranged. 
The heating of the camera was made with a warm air blower. Photo- 
graphs were taken of the test field with the camera lens in the tempera- 
tures -- 409 and — 30? C. Only plates of high flatness (Gevaert Avio- 
phot Pan 30) were used. 
The plates were measured in the autograph A7 nr 310 and the com- 
putations were performed according to the grid method, see the for- 
mula systems above. 
In Table 7 below the standard error of unit weight of the image 
coordinate measurements and the radial distortion amounts are demon- 
strated for different radii and for two plates, nos. 29 and 30 in high and 
low temperature respectively. No significant change of the principal 
distance was found. 
Evidently no significant effects upon the radial distortion or the 
standard error of unit weight can be found from this experiment, The 
radial distortion curves are demonstrated in Diagrams 9 and 10. 
Only the Eagle III camera and the Ross Xpress lens were tested in this 
30