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Re: [OM] Scanning B&W photos and the Callier Effect

Subject: Re: [OM] Scanning B&W photos and the Callier Effect
From: Winsor Crosby <wincros@xxxxxxxxxxxxx>
Date: Sat, 14 Sep 2002 13:32:08 -0700
-snip


On my Nikon 4000CN I've found that I need EXTREMELY fine grained negs to get
acceptable scans. Tmax400CN is supposed to be really fined grained and I
find it just barely acceptable for scanning... I have had pretty good
results with Fuji Acros 100.

I have given up on scanning color neg film unless I have no other option.
Transparencies all the way baby!

What results are other people seeing?

 - Matt Crawley


There is a common phenomenon called grain aliasing that makes a scan of a fine grain film look grainy when scanned. It seems to have to do with the relationship between the size of the film grain and the size of the pixels so that the way the scan sums things up the image is pixellated in a way that looks like exaggerated film grain. It is not really. It is a digital artifact. A rough way to think of it would be if you had a CCD that corresponded 1:1 exactly to film grain size. A smooth gray field in grain would yield a smooth gray field in pixels. If you decrease the grain size slightly, the first pixel will catch the smaller grain plus part of the space between the grains. Going down the line, eventually the center of a grain space will line up with the center of a pixel and you will get a light pixel Some where else you will get a darker pixel. Instead of a smooth gray field you will get a pattern of light and dark that will look like grain.

People will frequently experiment with different fine grain films to see which works best with their particular scanner.

At least that is my poor understanding of it.
--
Winsor Crosby
Long Beach, California


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