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[filmscanners] RE: Difficult scan problem

I apologize in advance here for just piggybacking on this post rather than
direct it directly to Rob; but it is conveniant and not that unconnected to
the discussion as a whole.

It just occurred to me - rightly or wrongly in this particualr case - that
this problem may be caused by the fluorescence light bringing out colors
that that the film is seeing which the naked eye does not similar to what
happens when one photographs a white object that has been whitened by
whitners which look white tot he naked eye but have a bluish cast on film.
Moreover, in traditional color photography, fluorescence lighting tends to
cast greenish, yellowish-green, cyan, or magenta color casts  depending on
the type of fluorescent tubes used; these color casts are often in need of
being filtered out either at the light source or at the lens (particularly
in the case of transparancies but often also in the case of color negative
films where it comprises the main or primary light source).  In addition,
the color shift or cast is typically global in nature which means that one
cannot keep the colors generated in one portion or object wiothin the image
while color corrected the other objects or portions of the image.  I suspect
that this would also be the case when scanning film taken under such
lighting.  Thus, it may be more than mere setting the white balance or even
after the fact color correcting if one is trying to keep the golden yellow
while eliminating the floro greens or blackish greens.

Just a random thought. :-)  Once again sorry to piggyback with this random

-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of michael shaffer
Sent: Monday, April 15, 2002 7:00 AM
To: laurie@advancenet.net
Subject: [filmscanners] RE: Difficult scan problem

Rob writes ...

> The negs are taken through a microscope and are of rocks.
> Some or every second one has been lit by fluorescence light
> source and the base colour comes out a golden yellow and
> the other colours are sort of fluro greens, greens to blacks.
> When the scans are done either in Nikon Scan or Vuescan they come
> out towards magenta tones.
> ...

  Most likely a white balance problem, and the fact neither software can
properly determine the "color of white" for a microscope illuminated
subject.  What Maris suggests should work ... that is, Vuescan's advanced
techniques should allow you to color correct a normal negative ... fix the
"mask correction", and then fix the "color correction".  These settings
could then be used to scan the problem negs.

cheerios ... shAf  :o)
Avalon Peninsula, Newfoundland
www.micro-investigations.com (in progress)

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