changes. The light leak causes areas of the film to
become fogged.
Exposure
A negative that has detail in both the shadow and
highlight areas is exposed properly. However, when
evaluating the negative image, it is necessary to
consider the subject matter because less exposure is
required for light sandy beaches and snowcovered
terrain and more exposure is required for dark terrain,
such as forests and industrial sites.
When you are viewing a negative that has been
exposed normally, patches of snow or light beach scenes
appear overexposed. Inversely, patches of dark terrain
or industrial sites appear underexposed. When the
negative is completely underexposed or overexposed,
the film sensitivity or filter factor (S/C) was set
incorrectly or the automatic exposure control (ABC) in
the camera system malfunctioned.
Vacuum
The lack of adequate vacuum in a serial-frame
camera permits the film to sag away from the focal
plane, causing the image to be blurred. The most
common indication of insufficient vacuum is crooked
data blocks.
Miscellaneous Defects
Reflections from the camera window of the aircraft,
depending on the angle of the sun in relation to the
window, can cause flare (nonimage-forming exposure)
of the film.
Condensation on a camera lens can result in a halo
effect surrounding film image points. This is generally
caused by rapid aircraft descent immediately before a
photo run.
AERIAL DUPLICATION
Two methods of producing high-quality
reproductions of black-and-white aerial film are in use
today. One method is the specific tone reproduction
method. The second method is simpler and more
feasible for shipboard use, so it is discussed in more
detail in this chapter. This method is called the
trigradient tone reproduction method or the 1.00 print
gamma method.
The following criteria is recommended as a guide
to optimum photographic quality and product
uniformity in producing duplicate positives or
negatives from original aerial negatives. The overall
objective of these recommendations is to ensure that a
maximum amount of intelligence information is
retained in an optimum form.
Only the straight-line portion of the
characteristic curve of the duplicating or printing
material must be used. For most duplicating film, the
straight line lies between densities of 0.40 to 1.80. Thus
the D-min should be close to 0.40 and the D-max should
be no more than 1.80 in the duplicate.
Normally, the contrast of the duplicate is correct
when the density range between the D-max and D-min
falls between 0.80 and 1.20, preferably near 1.00.
The requirement for using the straight line is met
when the exposure level of the printer is correct. The
contrast requirement is met when the processing is
correct. Specifically, the contrast of the duplicate can
be increased or decreased relative to the original by
increasing or decreasing gamma, respectively. To
achieve these goals, you must use some form of tone
control to guide the printing and processing operations.
The duplication of aerial reconnaissance imagery
requires that exacting standards and controls be
stressed. This helps to ensure that the imagery is of the
highest quality.
SPECIFIC TONE REPRODUCTION
METHOD
The purpose is to match the characteristic curve and
the density range of the original negative to the
characteristic curve of the duplicating material being
used.
TRIGRADIENT TONE REPRODUCTION
METHOD
The trigradient tone reproduction method of
duplicating is an objective method for determining
printing and processing requirements. This method
allows you to select one of three standardized processes.
Each process produces a different contrast or gradient.
The processing requirement is selected by determining
whether the density range of the duplicate should be
increased, maintained, or decreased. By doing so, you
can alter the density range of the imagery, if necessary,
in each generation. Thus the density range of the final
4-39

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