10 
3.2 
3.3 
3.4 
3.6 
3.7 
3.7.1 
VEILING GLARE 
Veiling glare shall be measured in the following manner or by a method from 
which equivalent results can be obtained. 
Test Field 
The test field shall be equivalent to an infinite uniformly bright Lambert’s 
Law surface containing a perfectly black spot. The black spot shall be circular 
and its diameter shall subtend an angle of 1? — 5' at the lens of the camera. The 
illuminant shall be that of section 1,4. There shall be no substance other than air 
between the test field and the lens or its attached filter. The black spot shall be at 
such a distance that the black centre of its out-of-focus image in the film plane of 
the camera is at least 1 mm in diameter. 
Photometry 
The camera shall be used to photograph this test field on the usual aerial 
emulsion held in the camera’s entire film plane in the usual manner. Well-control- 
led methods of photographic photometry shall be used to obtain the illumination 
of the centre of the image of the black spot and the average illumination 1° 30’ 
from it in the image of the bright field. 
  
NOTE: Light scattered back into the camera by the emulsion can contrib- 
ute significantly to veiling glare. Hence, any test method must provide a 
reflecting surface similar to unexposed film over practically the entire film 
plane. 
  
  
  
Field Angles 
The above measurements shall be made with the black spot on axis and at 
several other positions in the field, including positions near the edges and corners 
of the field. Any areas which might be affected by reflections from asymmetrical 
structures in the camera shall be investigated. 
Apertures 
Measurements shall be made at full aperture and at any other desired 
apertures. The apertures used shall be specified in the report. For full character- 
ization of a type of camera tests shall be made at three or more apertures except 
where the camera mechanism provides fewer than three apertures. 
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 shall be fully described in the report. 
Presentation of Data 
The quantity percent veiling glare is defined as follows: If /, total image 
illumination, that is image-forming light plus glare light as measured outside the 
image of the dark spot, and if I, = image illumination due to glare light alone, as 
measured at the centre of the black spot, then the percent veiling glare, V, is given 
by 
= 100 I, 
I, 
—— — — 4l