Re: A color space puzzle
Re: A color space puzzle
- Subject: Re: A color space puzzle
- From: "Bruce J. Lindbloom" <email@hidden>
- Date: Thu, 07 Feb 2002 09:24:05 -0600
Rolf Gierling wrote:
>
If you simplify it, X is a kind of red, Y a kind of green and Z a kind of
>
Blue.
>
>
But, by definition, Y is the luminance of the color, and both spaces have
>
the same white with a luminance of 1.
>
>
If you want to keep the luminance of the color unchanged, the conversion
>
G(sRGB) - Y - G(AdobeRGB) must result in the same values for green. So red
>
and blue must change.
BTW, I *do* know the answer to this puzzle (I would not have posed it as a
puzzle if I did not know the answer ahead of time).
I'm not sure I agree with your answer, though. The correlation between the
green channel and the Y ("kind of green" which is also the luminance) does
not have a bearing on the solution. The same behavior holds equally true for
any channel.
For example, if you started with a copy of sRGB and moved only the blue
primary to make a new working space, then converting an image from sRGB to
the new working space would preserve the blue channel data and change the
only red and green.
>
If you want to keep the luminance of the color unchanged...
The conversion from sRGB to Adobe RGB (1998) does not preserve luminance (Y)
except for neutral colors (R = G = B).
--
Bruce J. Lindbloom
www.brucelindbloom.com
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