[filmscanners] RE: Colour management on Negatives

["LAURIE SOLOMON" <laurie@advancenet.net>]

Bob,

All that you say is true and would need to be controlled and/or adjusted for
just as one would do when photographically printing a color negative and
color correcting with filtration for type of lighting (tungsten, daylight,
fluorescent, etc.).  However, for purposes of establishing an accurrate
color correction or adjustment for scanning purposes to be used as one's
starting point for any further color correction or enhancement to take care
of divergent exigent environmental factors caused by different location
lighting, I think that, as long as one shot the Macbeth color chart under a
standard lighting setup so as to produce a known norm for the type of film
being scanned, it should work as an approximation similar to what is done
with Shirley targets in the automated film labs.

>Perhaps a good white balance algorithm supplemented with white and gray
picker points would yield better results

I think that he is talking about accounting for differences in film brands
and types and their impact on the color renderings of scanners as reflected
in their outputs and not on the enviromental effects of different lighting
on the final colors rendered.  The latter would impact all films; whereas
the former  impacts would be confined to each particular brand or type of
film per se regardless of lighting.

-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Bob Shomler
Sent: Friday, August 15, 2003 5:36 PM
To: laurie@advancenet.net
Subject: [filmscanners] Re: Colour management on Negatives


>I suppose one could approximate what one can do with
>transparency film by shooting a Macbeth color chart and gray scale on
>the particular negative stock one wants to use, have the film processed,
>and then scan the film and have the software perform its reversal
>operation along with its accounting for the orange masking and its
>effect on the color rendition.  One could then compare the result in
>output of the finished scan with the original Macbeth color chart so as
>to determin what sorts of color corrections one needs to make to bring
>the finished scan into line with the original given the negative film
>being used.

Would this work through a range of different lighting color temperatures?
You might get a good usable set of color correction factors for a test case;
but unless one is working in studio environment or under controleld lighting
conditions it seems likely that subject incident light could vary from the
test environment such that those adjustments may well not produce color
fidelity through a range of lighting conditions.

Consider difference in conventional print color adjustments needed when
negative film subjects are illuminated by bright sunlight, deep shade within
bright sunlight (blue cast), and various indoor lighting (red cast from
tungsten).  Perhaps a good white balance algorithm supplemented with white
and gray picker points would yield better results.

Bob Shomler



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