Nikon D300 Complete Manual page 73

Sensors produce noise in two primary ways:
Thom Hogan's Complete Guide to the Nikon D300
Let's look at an even smaller
piece so that we can see the
noise. Now we're at 400%
view and the mottled nature of
the noise should be fully
apparent. Note that edges don't
seem very clear, and that
there's some false color
appearing in many areas
(almost like a prismatic effect).
Here we have the same image,
only partly corrected for
exposure in Photoshop and
then run through Neat Image to
remove most (but not all) of the
noise. The D200 fared much
worse than this, actually.
Indeed, most of the previous
Nikon DSLR bodies couldn't
approach the exposure levels I
was able to achieve in my gym
with the D300 (on the other
hand, the D3 wins hands down
over the D300 in this same
test).
And finally, the 400% view
with the noise cleaned up using
a double-dose of noise
reduction software. I did that to
clearly illustrate that we never
regain those edges when we
use noise reduction software.
Normally I wouldn't use noise
reduction software so heavy-
handedly, but I'm trying to
make a point: we can remove
noise, but not without other
issues intruding.
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