Re: [APML] Stacking

[Joe Pedit <pedit@email.unc.edu>]

George Anderson wrote:
> 
> I have searched the Kodak website to try and find the "typical" grain
> size for different films with no luck. I was looking to see what film
> had a grain structure that was similar to the size of the pixels in the
> ST-7. I realize that an exact comparison is not possible due to the
> natural randomness of grain shape and distribution versus the rather
> precise size and location of the sensors on a ccd.
> 

The noise we see in our images scanned from photographic film is
controlled by the film and the scanner.  See
<http://astro.umsystem.edu/apml/ARCHIVES/JAN00/msg00665.html> and
<http://www.photoscientia.co.uk/Grain.htm> for additional details.  The
noise in such images is not completely random.  There is a well defined
spatial structure to the noise that can be quantified.  Your question
brings up an interesting point:  Is the noise in CCD images completely
random (i.e., is the noise at one pixel location related to the noise of
its neighbor) or does a spatial structure exist?  A friend and I have
written a code that quantifies the spatial aspect of noise in tiff
images.  It would be interesting to try the code on a CCD image --
perhaps starting with a dark frame.

Joe

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