Table I. GUIDELINES FOR MEASURING 
CAMERA SYSTEM MTF'S 
Standard procedures for measuring camera system performance in terms of 
modulation transfer functions (MTF's) should yield results which are re- 
presentative of camera system capabilities under both laboratory and opera- 
tional conditions. In conducting such evaluations the following minimal 
conditions should be considered: 
a. 
Target: Edge (natural or man-made), bar, sinusoidal or line 
targets may be employed, providing the contrast ratio between 
the target and background is recorded on the straight-line 
portion of the film D-log E curve. Contrast ratios of 3:1 to 
6:1 are appropriate, with a low-light reflectance of approxi- 
mately 10 percent recommended. Spatial frequencies for bar and 
sinusoidal targets should range from approximately 2 to 60 cycles/ 
mm in sufficient increments to provide adequate data points to de- 
fine the MTF curve. Edge targets should have a minimum image size 
which is several times larger than either the effective slit of 
the microdensitometer or the spread function of photogrammetric 
camera system. Typical widths of photogrammetric camera system 
spread functions vary from 30 to 100 um depending on the film 
employed. 
Sensitometry: All evaluations should be conducted using the 
original film. Sensitometric data for the developed film should 
be obtainable from density measurements of a step tablet impressed 
on the film via a sensitometer prior to development. 
Microdensitometry: Microdensitometer parameters should be selected 
to avoid effects of coherence, noise and instrumental degradation 
of the system MTF. Typically, numerical apertures of the con- 
densing objective should be equal to or larger than that of the 
enlarging objective. Effective slit sizes of 1 x 80 um to 3 x 500 
um are recommended, with the smaller slits reserved for use with 
fine-grain, high definition imagery. 
Data Reduction: Reduction techniques involving the use of a com- 
puter are recommended, although close attention must be given to 
insure that the computational procedures yield consistent and 
reliable results. 
Final Results: Reports should include: date of photography, 
camera system and photographic parameters, processing procedures, 
analysis techniques/equipment, format location/orientation of 
target, methods of data reduction, and plots of modulation versus 
spatial frequency. 
camera system is taken to include camera-filter-film combination.