[filmscanners] RE: Scanner Profiling

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

Michael,

If I understand you correctly, I think I agree with what you say in theory
but do have a practical resevation or two about the import.

First, you use the term "absolute" as in "absolute color" in which you
assume we all know and understand what you mean and are using the same
definition.  This may or may not be the case; and you probably should have
explicitly defined your meaning and terms so everyone would be sure they are
on the same page as far as understanding what you are saying - this does not
mean that they will agree with your definition or meanings for those terms
or even your points and you may very well start a whole new debate. :-)

Second, as a purely mechanical-electrical device, a scanner does read and
capture colors within a given color space the same regardless of if it is
positive or negative film; but ( and these are big buts) green on a slide
represents green and is caputred as green while on negative film green
represents its complimentary color while being captured by the scanner as
green.  However, in the case of negative film, this green is compromised by
the addition of the color mask so it may not even present the same
uncontaminated green that positive film would present nor the exact
complement of its complementary color without some manipulation to remove
the film mask and uncontaminate the color.  Furthermore, most people think
about scanner captures and profiling and use those concepts in relation to
not merely the mechanical-electirical device and its phyusical operation but
to  the end results of that operation coupled with sanner software
manipulation (of which such things as drivers, profiles, and image capture
software is included) which does such things as mask removal from negative
films as well as conversion of the caputreed color on the film to its
complementary color as presented on the positive print or presentation.
Thus, a more technically specific discussion such as you offer may furnish
further clarification to some, it may also provide greater confusion to
many.

A point which to the best of my knowledge no one has made (in part because
this is a film scanner list even though many are scanning film with flatbeds
who are on the list) is that with flatbed scanners you do need two different
targets to profile the scanner for transmissive and for reflective
originals.  You cannot use the same target for both ( although the target
for both may consist of the same color patches and grayscale).  This,
however, is different than the negative/positive film distinction.

-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of michael shaffer
Sent: Wednesday, July 16, 2003 1:36 AM
To: laurie@advancenet.net
Subject: [filmscanners] RE: Scanner Profiling


Matthew writes ...

> What is the difference between a scanner profile (or target)
> and a film profile (or target)?

  Think in terms of absolute color.  Film, pos or neg, is already absolute
color, and to a scanner, it makes no difference if its pos or neg film.
What the scanner provides (as RGB) is not absolute color.  However, if the
scanner is accurately profiled (any method you choose, the keyword being
"accurate"), then its data becomes "absolute color" ... and what remains is
done in (color savvy) software.

  That's not to say, there's no such thing as "film characteristics".  If
you choose to profile with a film-specific IT8, I suppose you can say you're
profiling both, the film and scanner.  But that's not what the IT8's
reference file is for.  It describes the absolute color of each patch,
independent of film characteristics.  For profiling a scanner, all you
really want from an IT8 is (1) a full gamut of color (I read Fuji offers a
slightly larger gamut, but that's a different thread), and (2) an accurate
reference file.  Now you have accurate and absolute RGB data ... just what
you need for subtracting a mask and color reversal.

  It's no mystery why no one has not yet offered a negative-specific IT8.
It's not needed!

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


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