2.5.2 
2.5.3 
2.6 
2.7 
2.8 
2.9 
2.9.1 
2.9.2 
2.9.3 
2.10 
The collimator apertures and the positions of the collimators relative to the 
camera shall be such that the entrance pupil of the camera lens is filled with light 
from every part of the illuminated collimator field. 
Luminance shall be uniform over the collimator field and of the spectral 
quality specified in section 1.4. 
Number of Field Angles 
Targets shall be photographed at the principal point of autocollimation and 
along at least the two diagonals of the image format. They shall be photographed 
at a sufficient number of off-axis angles (at least 6 on a semi-diagonal) in each 
half field to permit accurate plotting of the distortion to the limit of the field. 
Filters 
Any filter normally used on the camera shall be in place during the test. If 
more than one filter may be used in service the camera shall be tested with each. 
Any filter used on the camera during tests shall be fully identified in the report. 
If its orientation on the camera is not well established by marks or indexing 
devices it shall be recorded in the report. 
Apertures 
Tests shall be made at full aperture and at any other apertures for which 
data are desired. The apertures used shall be specified in the report. For full 
characterization of a type of camera tests shall be made at three or more apertures, 
except where the camera mechanism provides fewer than three apertures. 
Negative Material 
The emulsion used should preferably be the same as is used in service. 
However, an emulsion of similar spectral sensitivity and gamma but with dif- 
ferent grain characteristies is acceptable, or any emulsion which gives equivalent 
results. 
For cameras in which the intended shape of the emulsion surface is a plane 
the emulsion shall be supported on a glass plate. Flatness of the plate at the time 
of exposure shall at least meet the tolerance for the flatness of the film plane 
in the camera under test. Preferably it should meet one-tenth of this tolerance. 
Alternatively the plate should be adequately stable, its unflatness should be 
measured and computational corrections applied. 
  
NOTE: For present (1960) accurate calibration it is desirable that the 
plate be flat, or its errors known, to — 1 micron (see section 2.13.2). 
  
  
  
For cameras in which the intended shape of the emulsion surface is not a 
plane, a plate of the intended shape shall be used, or a flat plate may be used and 
corrections applied if it is established that the corrections lead to results equivalent 
to measurements made in the intended surface. 
Exposure 
The exposure level shall correspond sufficiently closely to that used in 
practice to ensure that no significant errors in image position are introduced. 
  
NOTE: When the energy distribution in the spatial image is not sym- 
metrical, the apparent centre of gravity of the photographic image may be 
displaced by underexposure or by overexposure.