components of the residuals are plotted against the radius, some of them show 
a systematic variation with the radius. This type of variation ought to be com 
pensated for by the distortion parameters. There are perhaps not enough of 
them to do that. The radial distortion curves are corrected for the remaining ra 
dial components of the residuals and also transformed to the camera constant of 
256.000 mm. The resulting curves are shown in Fig. 15. It can be seen that pair 
no. 3 gives quite different curves. The difference between no. 1 and no. 2 will be 
tested. 
Fig. 14. 
Stereo-Medical-Nikkor, camera 2. Upper curve: radial distortion, dr, with a 95 °/o confidence 
interval. Lower curve: the radial part of the residual vector. From left to right the f-stop 
values are 45, 45, and 11. 
The standard error of the transformed radial distortion curve (sdr) depends on 
the standard errors of the computed distortion (s r ) and of the camera constant 
(Sc). 
r 2 
s 2 dr — s 2 r H r s 2 c 8.2.5 
c 2 
Here s c is the dominant factor. 
If the radial distortions are equal, the variable 
dr\ — dr 2 dri—dr 2 
]/s 2 dn + S 2 dr 2 5 
8.2.6 
54