Path: utzoo!utgpu!water!watmath!clyde!bellcore!decvax!tektronix!tekcae!kurtk
From: kurtk@tekcae.TEK.COM (Kurt Krueger)
Newsgroups: comp.graphics
Subject: Re: Color scanning of negatives
Keywords: I presume that the reference is to color film negatives.  There is the
Message-ID: <1464@tekcae.TEK.COM>
Date: 15 Feb 88 18:49:50 GMT
References: <333@inuxf.UUCP> <169@anumb.UUCP>
Reply-To: kurtk@tekcae.UUCP (Kurt Krueger)
Organization: Tektronix, Inc., Beaverton, OR.
Lines: 12

additional problem that a color negative also contains a mask - that orange
color.  This is compensated in the printing process by a sequence of filtration-
quite heavy filtration to be exact.  Filtration is done both to the light source
that passes through the film and then through a filter that is in the film
itself.  These filters (supposedly) are used to correct non-linearities in the
negative/film printing process.  In order to properly construct a positive
image, you will have to model this filtration/printing process, along with
these non-linearities.  It may be possible to scan the negatives through the
appropriate filters and construct a reasonable image.  It should be noted that
the filtration needs to be precise, and each negative requires a slightly
different filtration in order to generate a good positive.  Different types of
negative film require quite different filtration.