D65 vs D55 and a certain color

[Erland]

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.

[digitaldog]

Is there a white surround?

[Doug Gray]

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.

[xpatUSA]

. . . 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 muddy green is R,G,B = 101,116,50.

Armed with those numbers, we could head off to Bruce's Color Calculator.

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 . . .

[Erland]

According to this site muddy green is R,G,B = 101,116,50.

Armed with those numbers, we could head off to Bruce's Color Calculator.

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?

[Doug Gray]

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.

[Peter_DL]

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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