RE: filmscanners: Profiling negative films

["shAf" <michael@shaffer.net>]

Alan writes ...

> Due to the variation in mask on negative films from batch to
> batch and development to develope of individual rolls, a profile
> like is done with an IT-8 on slide film doesn't work too well.
>
> BUT it occurred to me on film scanners that do NOT have the
> ability to vary their exposure that perhaps profiling the IT-8
> and then taking a RAW scan from VueScan through this profile and
> then back into VueScan might produce a more consistant image?

        I believe you may be of the mistaken notion that a profile is mostly 
about
getting the color right.  Certainly, this is a big part of it and makes
subsequent correction easier ... however, the most important aspect of a
scanner's device profile is the color gamut it is capable of, to a degree
independent of getting the color right.  The gamut is important because it
isn't something we can easily evaluate ... not until we've put the RGB data
through extreme adjustments and then finally to hardcopy do we ultimately
realize the scanner didn't capture something that was on film.
        You have to present the scanner with a special color target for 
profiling
its color capabilities.  A Kodak Q60e is a good start, but I've heard you
need something other than one of the dupes generally distributed.  Still, if
Ed properly measures the scanner's color capability and therefore makes RGB
data representative of the color which was on film, then you are more than
halfway there ... what remains is simply color correction.

        Which isn't to say Ed has a few issues to work out.  Ed may have more to
say, but I believe his evaluation of Q60 target results only in a
matrix-type profile, which, generally is a simplification of a device
profile.  Still, what you pay for Vuescan doesn't warrant any more than a
simplified determination of the scanner's color capabilities ... and what Ed
provides, short of getting the color "exactly" right, will get you past 99%
of every film exposure ... slide or negative.

my US$0.02 ... shAf  :o)