(113) 
llimator. The col- 
the apparent per- 
ie collimator relat- 
upil of the camera 
c. 
m by illuminating 
le collimator tube. 
ffects of veiling 
of veiling glare 
>n of glare cor- 
, from measure- 
wer can be cal 
lable by camera 
:ms desirable to 
it exceeds per- 
;enerally used in 
,t a sufficient num- 
>aration of reliable 
to the limit of the 
. Other focus set- 
on of a camera (or 
; sufficient to ensure 
best average reso- 
is shall be establish- 
iringe focus for the 
f the photographic 
al minimum fringe 
of an opaque edge 
of transition from 
il image through a 
ally be mounted so 
i camera is parallel 
entation used shall 
1.8 Filter. 
If a filter correcting for vignetting and cos 4 effect is normally used 
on the camera it shall be in place during the test. The use of any other 
operational filter on the camera during test is optional. Any filter 
which is used shall be fully described in the report. Preferably its 
transmission curve should be given. 
1.9 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 (or lens) tests 
shall be made at three or more apertures. 
1.10 Emulsion. 
The camera (or lens) shall be tested with the same emulsion as is 
used in actual practice, or one which is closely equivalent. If it is neces 
sary that the usual test emulsion differ slightly from the service emul 
sion, typical tests shall be made with both emulsions and all reports 
shall indicate the magnitude of the error introduced by the emulsion 
change. The emulsion or emulsions involved shall be specified in the 
report. 
1.11 Exposure. 
The same exposure (object luminance and time) shall be used at 
all field angles. It shall be that exposure which gives best average 
resolving power. 
1.12 Development. 
Development shall be a well controlled equivalent of the average 
found in actual practice. The gamma shall be 1.25 ± 0.20. The devel 
opment procedure shall be stated in the report. 
1.13 Reading. 
1.13.1 When reading the target images, magnification and illumination 
shall be adjusted to obtain maximum resolving power values. A low 
power stereoscopic microscope will be found suitable for most reading. 
1.13.2 Resolving power shall be stated in lines per millimeter relative to 
a flat distortion-free image. When the ratio of the camera and colli 
mator focal lengths is being used to compute the resolving power at 
the image which corresponds to a certain size of test object, correction 
off-axis shall be made only for the “cos” and “cos 2 ” factors affecting 
resolving power values on radial and tangential lines. No allowance 
shall be made for image size changes due to the use of a curved focal 
surface or the introduction of large amounts of distortion. 
note: If a lens is deliberately designed with large negative dis 
tortion to improve field of view or image illumination the 
resolving power values which can be obtained by actual measure 
ment of line separations in “compressed” areas on the film are 
misleadingly large. These areas have to be expanded before use to 
give a distortion-free image as is obtained in conventional 
systems. This expansion reduces the resolving power.