>. 
current report (Norton, et al., 1976). These guidelines are intended as 
à procedural framework rather than as standards, and are based on analyses 
of aircraft and satellite images conducted by several investigators. The 
philosophical and technical implications of MTF analysis techniques as re- 
lated to the prediction and measurement of photographic and electro-optical 
system performance are considered in this report. A recommendation con- 
cerning the future activities of the OTF/MTF Working Group is also presented. 
PHOTOGRAPHIC SYSTEMS 
The image recorded by a photographic system is degraded by the lens, 
film, image motion, atmosphere and reproduction process, and for theoreti- 
cally correct assessments all of these factors must be taken into account. 
In practice, however, the lens, film and image motion control the quality 
of first-generation aerial photographs recorded by a photogrammetric camera 
system. An MTF (which illustrates the reduction in contrast that occurs 
as a function of spatial frequency (v) when a sinusoidal target is recorded 
by an imaging system) can be computed for each of these components and a 
total system MTF predicted with the following equation. 
MTF (v) = MTF(v) x MTF(v) x MTF(v) 
system lens film image motion 
v = spatial frequency in 
cycles/mm 
This well-known cascade process is illustrated in Fig. 1 for a typical 
photogrammetric camera system. Correspondingly, system MTF's can be de- 
rived from microdensitometer traces of targets recorded on operational 
imagery, and these measured MTF's compared to the predicted values to 
assess operational system performance. Because photogrammetrists and photo- 
interpreters normally prefer to evaluate system performance in terms of re- 
solving power, several techniques have been derived for determining reso- 
lution values from MTF's (Charman, 1975; Artishevskii and Chalova, 1976; 
Brock, 1976). Some principal methods for the prediction and measurement 
of system performance are summarized in Table II. 
Of the technqiues listed in Table II, methods 2 and 3 are frequently 
used to assess photographic system performance. However, as with resolu- 
tion, objections are occasionally raised concerning the reliability of MTF 
analyses, particularly with respect to: 
a. Errors or variations in the MTF's of lenses and films due to 
non-standardized measurement techniques and variable development 
conditions. 
Non-linearity of the photographic process. 
Target fidelity. 
Degradations introduced by the microdensitometer and film 
granularity. 
In the following paragraphs these factors are considered in relation to 
practical photogrammetric camera system performance evaluation.