RE: Re: a colorspace quandry
RE: Re: a colorspace quandry
- Subject: RE: Re: a colorspace quandry
- From: "email@hidden@pop3.grafixgear.com" <email@hidden@pop3.grafixgear.com>
- Date: Sun, 15 Apr 2001 07:35:50 -0400
>
No, the scanner profile describes the performance of the CCD and its
related circuitry
There seems to be a bit of confusion. I think what Bob implied could be
said in this way. -The scanner profile is a description of a system which
includes the film gamut, the CCD (or PMT) and related hardware/driver
pieces: and therefore creates a corrective bit of math which helps the
system to "see" the way the human eye would see that film.
Once the scan is converted from raw using the input profile to a more
neutral flavor of RGB using a working space destination (or alternately
to Lab), then we have created a fairly accurate reproduction.
As Ektachrome is a component in system 1 and Fujichrome is a
component in system 2, separate profiles would be built. Remember,
we must train the scanner to see those emulsions the way our eyes
work.
>
Perceptual transforms will squeeze data down from a larger space
to maintain color relationships in a smaller space. It won't expand data
when moving to a larger space.
I have not heard anyone previous to this point articulate that perceptual
rendering can only reduce gamut. I would be interested in hearing if
that is the case with all manufacturer's use of this transform.
Part of the problem with using a matrix-based working space is that
the system is based on RGB phosphors. The space must be larger
than the scan system. Think of stretching a three corner tent over an
oval shape in order to cover it.
The point made about a LUT-based working space is that in converting
from an input profile to a LUT space, some of these perceptual issues
are mitigated.
There was clearly a misunderstanding about a LUT working space.
One does not use the input profile as the working space. Once
converts to a space such as Joe Holmes Ektachrome space, which
Joe produced as a LUT-based space.
- Jon
--------------------------------------------------------------------
Mail2Web - Check your email from the web at
http://www.mail2web.com/ .