the gamma for the plot is 0.82.
density between the useful shadow and highlight
densities in a negative. Total negative contrast is a
useful index to determine what contrast printing filter
to use. Total negative contrast is dependent upon
factors, such as subject luminance ratio, camera
exposure level, color of light, and gamma. Gamma is
only one of the factors that controls the total contrast
of a negative. In addition, a negative has other forms
of contrast as follows:
section of the characteristic curve and,
therefore, unrelated to gamma.
shoulder of the characteristic curve and
gamma does not apply.
straight-line section of the characteristic curve.
for example, 0.75. However, each negative probably
has a different total contrast because of variations in
forth. "Contrast," therefore, is best defined as a range
of densities produced by a combination of the subject
luminance ratio and the amount of development given
gamma (for example, 1.6) and still produce a flat
negative, because of the small luminance range of the
subject being photographed. Another scene with a
high-luminance ratio could be photographed and
developed to a low gamma of say 0.50, yet the
contrast of the negative could be so high that it
requires a low-number contrast printing filter.
little contrast in the shadows when those shadows fall
on the flat portion of the toe. When two films with
the same characteristics are exposed to the same
scene, at the same time, and each film is developed to
a different gamma, more contrast can be expected in
the negative developed to the higher gamma. This is
true for those tones exposed on the straight-line
section of the characteristic curve and to a lesser
extent for tones exposed on the upperpart of the toe.
negative and subject contrast. A negative that is
developed to a gamma of 1.00 has, for all straight-line
exposures, the same contrast range as the original
scene. When the negative is developed to a lower
gamma (for example, 0.50), it has only half as much
contrast as the subject. Remember, this applies only
to the straight-line section of the curve.
Gamma does not take into consideration that the toe
of the curve is normally used for recording shadow
tones in ground pictorial, continuous-tone film. Also,
D-log H curves for different films have different toe
lengths and toe shapes; consequently, film developed
to a given gamma may not yield a uniform density
range sufficient enough for ordinary continuous-tone
photography. To provide a more uniform density
range, you can use a form of averaging the gradient,
called contrast index. However, in some applications
where the characteristic curve has a long straight-line
straight-line section of the curve, gamma is still a
valid method of measuring density range.
straight-line section of the characteristic curve. When
all subject tones are recorded on the straight-line
section of the curve, the greatest amount of tone
separation is obtained in all areas of the image
(shadows, midtones, and highlights). This provides
Advanced Photography Course