Contrast Parameter - Nikon D300 Complete Manual

V1.02

Contrast Parameter

By changing Contrast in a Picture Control you tell the
camera what kind of exposure curve to apply to the sensor
data. You may remember a footnote back in the sensor
section where I pointed out that a digital sensor is more
regular in capturing brightness values than film. The "normal"
regularity is a curve that rapidly rises in the dark values but
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tapers a bit as it reaches the bright values . Tone
compensation changes the slopes of that curve, which shows
up to our eyes as image contrast.
Choosing a lower number (less contrast) tends to "flatten" and
"narrow" the curve (and narrow the resulting histogram),
resulting in considerably less overall scene contrast, often at
the expense of rich blacks. Choosing a higher number (more
contrast) tends to exaggerate the curve (and widen the
resulting histogram), producing distinct blacks and whites
(which may be blown out) with less subtle gradation in
between. 0 is obviously between these two extremes. The A
(automatic) setting uses the camera's matrix meter to take a
guess at how to set contrast. If it sees large differences in
brightness values, the camera may think it's dealing with a
high contrast scene and lower the contrast (think about that
statement; it's correct). Likewise, it might do the opposite if
there are few or small differences in brightness values across
the scene.
The final option, USER, appears if you've used Camera
Control Pro 2 to create a Custom Curve. This parameter isn't
selectable or changeable from the camera. See the
Introduction to Nikon Software eBook that came with this
Complete Guide for details on creating Custom Curves.
For JPEG images, you absolutely need to set something, with
0 being the default choice for the predefined Picture Controls.
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Okay, that's a gross simplification. I wrote a long article in my Nikon DSLR Report,
Issue #5 that describes in gory detail the "normal" way in which brightness values
becomes bit values, if you're so inclined to get beyond the simplification.
Thom Hogan's Complete Guide to the Nikon D300 Page 354