Nikon D300 Complete Manual page 77

V1.02
You'll note just a hint of amp noise in the upper left and lower
right corner. In general, Long exp. NR does a perfectly fine
job of getting rid of this. And under in most conditions at
which you'd shoot, you shouldn't find any amp noise in your
D300 shots.
Finally, since the D200 appeared with "banding noise" issues,
I need to address the notion of "pattern noise." With film, the
individual grains in the light-responsive layers were
essentially ordered randomly. Thus, when grain became
visible (say in a very large print), it had no distinct pattern to
33
it .
With digital, the photosites are most decidedly not laid out in
random patterns. They are on a fixed grid and in fixed
positions. Moreover, there are additional patterns on a sensor,
most notably the power lines and readout connections. The
location of electron wells and the photodiodes they relate to
have fixed relationships.
All this means that certain types of noise can have patterns in
them. Shot noise doesn't, for example, since it is a random
variance of photon detection. But read noise often does, as
does dark current noise. What the pattern will be and how
visible it is depends upon a number of factors. In general,
33 Even those that argued that some grain seemed "clumped" were only seeing
stochastic random patterns.
Thom Hogan's Complete Guide to the Nikon D300 Page 77