RE: color mapping
RE: color mapping
- Subject: RE: color mapping
- From: "Marc Aguilera" <email@hidden>
- Date: Sat, 07 Jul 2001 16:56:33 -0700
The Question:
> What in simple terms is the difference between absolute and relative
> colorimetric
> rendering intents? Also Perceptual?
Fred Bunting Wrote:
When you ask for 'Colorimetric' rendering, you are saying, "preserve the
colorimetry (the color as measured by a colorimeter) of the original
sample at all costs."
Absolute Colorimetric is the most extreme form of this. It says, "even
if the original and reproduction use different substrates (e.g.
different papers), make them match colorimetrically (if possible)." So
if the original was printed on yellowish paper compared to the
reproduction paper, the Absolute Colorimetric rendering will add some
yellow to the color as it renders it. We are interpreting the colors
relative to some absolute white point ... usually the white point of the
illuminant lighting both samples.
Relative Colorimetric relaxes the restriction a bit by allowing the eye
to adapt to the different substrates. It says "find the relationship
between the original sample and its paper, and preserve that
relationship in the reproduction (if possible)." So "white" means "the
color of paper", even though this white may be different between the
original and reproduction medium. We are interpreting the colors
relative to their respective paper whites.
Perceptual rendering says "preserve the perceptual relationships
*between* the colors (as much as possible), even at the expense of
colorimetry." This is intended for images, where if some of the colors
are rendered with colorimetric accuracy while some others have to be
remapped (because they are out of gamut), you get a bad image.
Well stated, as it should be!
Marc Aguilera
ColorBlind Software
www.color.com
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