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6.7 Aperture 
Ihe apertures used in the measurements shall be stated in the 
report. 
6.8 Presentation of Results 
The results shall be presented in the form of tables showing 
the value of modulation transfer function (and phase transfer function 
if measured) at each spatial frequency, for each field angle, azimuth, 
and focal position tested. If preferred, results may also be shown 
as graphs of transfer function versus spatial frequency for each 
focal position, field angle, and azimuth. For some purposes, it 
is best to use double logarithmic paper, but this is not universally 
So, and the presentation of tabular data will allow the user to 
select his own preferred method of plotting. 
6.9 Guidelines for Measuring MTFs of Camera Systems 
Standard procedures for measuring camera system performance 
(camera-filter-film combination) in terms of modulation transfer 
functions (MTF's should yield results which are representative 
of camera system capabilities under both laboratory and operational 
conditions. In conducting such evaluations, the following minimal 
conditions should be considered: 
6.9.1 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 appro- 
priate, 2 to 60 cycles/mm, in sufficient increments to provide 
more than 5 data points. 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 the photogrammetric 
camera system. (Typical widths of photogrammetric camera system 
Spread functions vary from 30 yum to 100 um depending on the film 
employed.) 
6.9.2 Sensitometry: 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. 
6.9.3 Microdensitometry: Microdensitometer parameters should 
be selected to avoid effects of coherence, noise, and instrumental 
degradation of the system MTF. Typically, numerical apertures 
of the condensing objective should be equal to, or larger than 
that of the enlarging objective. Effective slit sizes of 1 um 
x 80 um to 3 um x 500 um are recommended, with the smaller slits 
reserved for use with fine-grain, high definition imagery.