9 
The mechanical supporting equipment of this projec 
tion system provides 6 freedoms of exterior orientation 
which allow its use for vertical, and transverse oblique 
photography well within the tilt range that is generally 
considered applicable to superwide angle photography. 
A number of test results of laboratory and opera 
tional tests are available now which form a fairly good 
basis for appraisal of the service performance of the 
Balplex 120° system. It deserves mentioning, that there 
is a pleasing agreement between optical bench tests of 
resolution and distortion established in practical pro 
jection tests of a series of 12 projectors using reso 
lution targets, grid and terrain plates. The following 
test results, which may be considered representative 
have been established. 
a. Resolution in lines/mm using a USAF high con 
trast target with a progression of line 
blocks of opaque lines on clear background. 
TABLE I 
Proj.Distance 0° 20° 30° 45° 55° 
320mm 
40 
60 
55 
40 
32 
390mm 
90 
80 
75 
60 
48 
460mm 
64 
45 
35 
32 
32 
Radial distortion 
in microns 
at 
nominal 
jection distance of 390mm, average of 18 com 
pensated red and blue lenses. 
0 
20 30 
TABLE II 
40 50 55 60 
-0 
0 
-2 
0 +2 +6 
-9