Luminous Landscape Forum
Raw & Post Processing, Printing => Colour Management => Topic started by: Erland on December 17, 2015, 05:14:16 am
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Hi!
I was talking to a customer right now, who wanted me to calibrate their screen to D55 and 120cd. No problem, and While I was doing this, he asked whether a certain color, lets say Muddy green, will look the same on both D65 and D55 as whitepoint? Will the whitepoint alter the appearance of darker colors? I told him that I don't think so, and that the whitepoint don't affect the primaries and hence not the colors in between? But I can't say I am that very sure of it.
Kind regards.
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Is there a white surround?
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Hi!
I was talking to a customer right now, who wanted me to calibrate their screen to D55 and 120cd. No problem, and While I was doing this, he asked whether a certain color, lets say Muddy green, will look the same on both D65 and D55 as whitepoint? Will the whitepoint alter the appearance of darker colors? I told him that I don't think so, and that the whitepoint don't affect the primaries and hence not the colors in between? But I can't say I am that very sure of it.
Kind regards.
If you measure it they will differ. If it's a patch on a white (255,255,255) background it will look the same as long as you don't have another monitor nearby set up with a different WP. Your eyes adapt to the white and you interpret colors based on that. If you have different monitors it can be quite confusing to glance at each.
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. . . While I was doing this, he asked whether a certain color, lets say Muddy green, will look the same on both D65 and D55 as whitepoint?
According to this site (http://hex.wikimix.info/en/color-657432) muddy green is R,G,B = 101,116,50.
Armed with those numbers, we could head off to Bruce's Color Calculator (http://www.brucelindbloom.com/index.html?ColorCalculator.html).
There we find that D65 gives x,y = 0.368886, 0.468756
and that D55 gives x,y = 0.384116, 0.475451
CIE xyY model, of course. Like the well-known 1931 gamut diagram.
Also they are 2 degrees different in L*a*b* hue angle.
No idea if they would 'look the same' on an emissive device like a monitor.
Might investigate further . . .
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According to this site (http://hex.wikimix.info/en/color-657432) muddy green is R,G,B = 101,116,50.
Armed with those numbers, we could head off to Bruce's Color Calculator (http://www.brucelindbloom.com/index.html?ColorCalculator.html).
There we find that D65 gives x,y = 0.368886, 0.468756
and that D55 gives x,y = 0.384116, 0.475451
CIE xyY model, of course. Like the well-known 1931 gamut diagram.
Also they are 2 degrees different in L*a*b* hue angle.
No idea if they would 'look the same' on an emissive device like a monitor.
Might investigate further . . .
Thanks! I find it rather odd though. I thought the rgb primaries remained the same and thus the colors ( at least the saturated ones) even when shifting whiteprint.
Wouldn't that make viewing pantone colors that are within gamut appear with a color shift?
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Thanks! I find it rather odd though. I thought the rgb primaries remained the same and thus the colors ( at least the saturated ones) even when shifting whiteprint.
Wouldn't that make viewing pantone colors that are within gamut appear with a color shift?
When you change the white point, the profile adjusts the maximum intensity of each primary so that (255,255,255) produces the desired white point. As a result other colors are scaled and changed in proportion.
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When you change the white point, the profile adjusts the maximum intensity of each primary so that (255,255,255) produces the desired white point. As a result other colors are scaled and changed in proportion.
to expand on this, the linear scaling of X/Y/Z - from source white to target white and across all colors - is part of the Chromatic Adaptation Transform which is part of the RelCol rendering from the working space to the monitor profile.
As for the math part:
http://docs-hoffmann.de/cmsicc08102003.pdf
http://www.brucelindbloom.com/index.html?Eqn_ChromAdapt.html
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