Digital BW, The Print

Noise is a constant amount, plus a part that is proportional to
exposure time. Longer exposure, more noise from Dark Current.  The
answer is to take multiple exposures and co-add them in
post-processing. Working from a stable mount, like a tripod, the
images will register if there is no movment in the scene or from the
camera. Generaly losest noise is when the readout noise and the dark
current noise are equal in each shot.

You are not moving the film etc, so there is no need for overly
long exposures in the camera.

-- 
Paul Repacholi                               1 Crescent Rd.,
+61 (08) 9257-1001                           Kalamunda.
                                             West Australia 6076
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