[Leica] Shadow noise in scans

[abridge at gmail.com (Adam Bridge)]

The most informative information about your scan isn't included: the
histogram from VueScan. I suspect that there's a lot of information
way off to the left (dark) side of the histogram so that when you
widen the histogram with curves and levels, even using 16 bits of
data, lots of pixels get "created".

Adam

On Sat, 14 Aug 2004 23:41:18 -0700, Peter Klein <pklein@2alpha.net> wrote:
> Folks:  I frequently encounter shadow noise in my scans. I can usually work
> around it, but I'm wondering if there is something I can do--perhaps while
> scanning--to minimize it.
> 
> Have a look at this:
> http://users.2alpha.com/~pklein/temp/noise.jpg
> 
> This picture was taken with an M6TTL and CV 50/1.5 Nokton, on Kodak T400CN
> rated 400.  It was taken in a dim reception hall, but the subjects were
> illuminated by a shaft of light from some nearby large windows, and I
> exposed for them, not the background.  The scanner is a Canon FS-4000, run
> at 4000 dpi and driven by VueScan.  I scan to 16 bit TIFF, and use Picture
> Window Pro in 16 bit mode for my editing.  The various versions of the
> picture are shown at 1/3 actual pixels.
> 
> The leftmost image is of the scan pretty much out of the scanner (I'd
> spotted and cropped, but that's all).  You can see the noise in the darkest
> areas.  This is the kind of noise I am often plagued with.  It tends to
> happen more often in available light pictures than well-lit outdoor
> shots.  It doesn't show much on a 5x7 quadtone print, but is quite
> prominent on an 8x10.  And if I get the same negative printed in a wet
> darkroom, the noise isn't there.
> 
> The center image is what I ended up with after curves, contrast, and
> sharpening (the latter using a mask so only the people were sharpened, not
> the surrounding area).  I've dropped the background to nearly jet-black,
> but there are still lots of noise speckles.  And I've lost some gradation
> in the girl's hair.
> 
> The righthand image has been noise-filtered with NeatImage before curves,
> etc.  I used it sparingly so it wouldn't soften or "plasticize" the image
> too much.  It's helped, but the noise still shows up--more in a print that
> on the screen.  I've found that most of the time, when I use NeatImage or
> Picture Window's Despeckle feature, I can only get rid of some of the noise
> before the image gets messed up.
> 
> What might I try to get rid of this noise?  Is there anything can I do to
> minimize it during the scan?  I've tried the multiple exposure feature in
> VueScan, and it doesn't really help with this type of noise.
> 
> BTW, here's the whole picture.  This one is a reduction of the Costco CD
> Jpeg I got when the film was developed.  They went way dark, so you see no
> shadow noise (or detail).
> http://users.2alpha.com/~pklein/JonAntionWedding/Show/JonAntionWedding/slide_13.jpg
> 
> Thanks,
> --Peter Klein
> Seattle, WA
> 
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