Re: On ProPhotoRGB
Re: On ProPhotoRGB
- Subject: Re: On ProPhotoRGB
- From: bruce fraser <email@hidden>
- Date: Mon, 27 Feb 2006 08:34:04 -0800
Don RGB and ECI RGB are good for film scans, but
digital captures routinely contain colors (bright
yellows and oranges, dark greens and browns are
the main culprits) that are clipped by either
space.
2D plots of 3D spaces always require careful
interpretation. With a huge space like ProPhoto,
plotting the extremes in Lab or Luv can be quite
misleading for several reasons.
You certainly aren't going to capture these
colors, and while it's possible to drive 'color'
there artificially, it's not really something
anyone in their right mind would come close to
doing.
When Lab and Luv were developed, the available
gamuts were quite small, and Lab and Luv behave
well in terms of both perceptual uniformity and
having straight lines represent constant hues.
When you extend the gamut, the spaces break on
both counts. When you extend the gamut to the
imaginary primaries used by ProPhoto, you're
trying to plot things in Lab and Luv that are
outside the models, so you get nonsensical
answers.
The weirdnesses Marco has posted are as much
about the limitations of Lab and Luv as they are
about any actual issues with ProPhoto. In my
experience (I've been using ProPhoto since it was
ROMM RGB, so about 7 years now), they don't
represent a problem in the normal practice of
reproducing images.
I have a growing library of digital captures that
really suffer when they're converted into smaller
spaces than ProPhoto because gradations of
saturated color get clipped to blobs, and once
they're blobs it's very difficult to map them in
an acceptable manner into an output space. It's
not about trying to maintain colors I can't
possibly reproduce-it's about maintaining the
distinctions between those colors, so that I can
map them into output space as gradations rather
than as big blobs of solid color....
Bruce
At 11:17 PM +0100 2/26/06, Karsten Krüger wrote:
Hi Marco,
Nice job :-)
Did you do the same with ECIrgb and LStar-RGB ?
Both are recomended workingspaces for digital
photography when targetting print. They are
supposed to match ISO cmyk gammut without too
much loss. They both have the same primaries and
gammut, but differ internally. ECIrgb is has a
gamma of 1.8 while LStar-RGB is linear to
L*-axis. What is your opinion on them ?
www.eci.org
www.lstar-rgb.com
Thanks,
Karsten
Am 26.02.2006 um 05:10 schrieb Marco Ugolini:
Hi to all.
While viewing ProPhotoRGB with the ColorThink grapher, I noticed something
that has not yet been discussed in this forum, to my knowledge.
Please go to my web page to view a few images first, before I go on:
<http://home.mindspring.com/~marcoug>
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