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The CIE XYZ and xyY color spaces - new technical article

Doug Kerr

Doug Kerr

Well-known member
We often see references to the CIE XYZ color space, and frequently use its cousin, the CIE x-y chromaticity plane.

The CIE XYZ color space is the standard scheme used in color science to describe the color of light, essentially sort of the "metric system" way of doing that.

We use it (through its derivative cousin the CIE x-y chromaticity plane) to define the primaries used by the various "additive" color models, such as sRGB and Adobe RGB. But how would we define its primaries?

In fact, its primaries are imaginary - we cannot generate or emit them, and if we could, we could not see them. How then can they be the premise for "precisely" defining the color of real, visible light? And how can it be that the value, Y, of the amount of one of the primaries is always exactly the luminance of the color represented? Are the other primaries "impotent" insofar as a contribution to luminance? (Yes.)

As a real "working" color space, it plays a role in the application of ICC color profiles.

The story is fascinating. It is laid out in my new technical article, "The CIE XYZ and xyY Color Spaces", available here:

http://dougkerr.net/Pumpkin#CIE_XYZ
 
D

Damien Paul

New member
ah, my 2 favourite colour spaces... I have been using these alongside their cousin CIE Lab, CIE Yuv (as well as du' and dv' from an awesome earlier article by you, Doug), CIE Luv, CIE LCH... I have so many graphs and charts for my data that I fear that my MSc will be about 70 pages of writing, 25 pages of bibliography and 100 pages of graphs (it is actually heading that way).
 
B

Bart_van_der_Wolf

pro member
Doug_Kerr said:
The story is fascinating. It is laid out in my new technical article, "The CIE XYZ and xyY Color Spaces", available here:

http://dougkerr.net/Pumpkin#CIE_XYZ
Click to expand...

Hi Doug,

Thanks for the new article. I'll have to read it first before I can comment.
The following page may also shed some light on the use of the xyY CIE chromaticity diagram, especially when trying to avoid the pitfalls of a 2 dimensional representation:
http://www.brucelindbloom.com/ChromaticityGamuts.html .

Cheers,
Bart
 
Doug Kerr

Doug Kerr

Well-known member
Hi, Bart,

Bart_van_der_Wolf said:
The following page may also shed some light on the use of the xyY CIE chromaticity diagram, especially when trying to avoid the pitfalls of a 2 dimensional representation:
http://www.brucelindbloom.com/ChromaticityGamuts.html .
Click to expand...
Yes, that is very useful. Thanks for the reference.

The issue of course is that of attempting to present the color gamut of (for example) a color space with the CIE x-y chromaticity diagram (a doomed enterprise, the result of which we all-too-frequently see "committed").

Fortunately, that "difficulty" does not arise when using the x-y chromaticity diagram to present the chromaticity of a particular color (for example, that of a particular instance of light, actual or hypothetical).

All of Bruce's stuff is so useful. When I am working on colorimetric matters, I keep at least one browser instance "permanently" open to his site.

Thanks again.

Best regards,

Doug
 
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