method for calibrating aerial cameras was not considered seriously 
for some time. By experimenting with a number of filter and light 
combinations, however, we found that we could approximate the cali 
brations obtained with the field range and multicollimator if the 
target plates were adequately illuminated. A combination of No. 73 
Wratten filter and a flourescent light source provided optimum 
results. 
TEST PROCEDURES AND RESULTS 
CORRELATION 
Since lens calibration data obtained from the goniometer when 
using the fluorescent light source and a No. 73 Wratten filter appeared 
to closely approximate the calibration data obtained from photographic 
methods, we conducted a series of tests to see how closely the two 
methods correlated. Camera lens Type T-ll, No. XF-2256, was selected 
for the tests. Closely correlated calibration data already were available 
on this lens from the Fairchild Camera and Instrument Corporation's 
multicollimator and from the field calibration range. Results of 
these calibrations are presented in Table 1. 
When comparing the results of calibrations in Table 1, a maximum 
deviation of 10 microns appears between the radial distortion curves 
for the goniometer and the multicollimator. The maximum deviation 
between the curves for the field range and the multicollimator is 
3 microns. 
REPEATABILITY 
Further tests were conducted to determine whether the same precision 
could be obtained with repeated tests. Data was first recorded when 
using the No. 73 Wratten filter and a tungsten light source. Results 
of each of the calibrations were tabulated, and curves were drawn from 
an average of the four diagonal halves for each. These curves show that 
75 percent of the targets fall within +1 micron and 94 percent within 
+3 microns of the average deviation. The remaining 6 percent of the 
targets, measured at angles of 45°27' and 46°40', fall within 5 to 6 
microns of the average. 
Similar calibrations were made on Type KC-1 camera lens cone 
No. XF-6765, using the goniometer with a No. 73 Wratten filter and a 
fluorescent light source. Four individuals recorded the results of 
seven observations. Plots of these readings indicated that 76 percent 
of the points fall within +1 micron of the mean and 97 percent within 
+3 microns. In addition, 84 percent of the readings of each diagonal 
fall within +3 microns of the mean. The adjusted average distortions 
for each observer and the mean for the group are presented in Tahle 2; 
the mean is plotted as a single distortion curve in Figure 4, as com 
pared with the multicollimator calibrator.