Re: D50 definition

There are many sources for 96.42, 100, 82.49

Bruce Lindbom’s site is inconsistent.
 http://www.brucelindbloom.com/index.html?ColorCalculator.html doesn’t return any numbers like these for D50 or 5003K
One cause is inadequate precision. As some sources go from 4-decimal xy to XYZ, the error in XYZ could be +- 0.0003
Another cause is legacy. D50 might have been defined before all other math was completed. Just like the speed of light.
Thanks,
Lars Borg  |  Principal Scientist  |  Adobe  |  p. 408.536.2723  |  c. 408.391.9479  |  borg@adobe.com


On 4/2/18, 10:19 AM, "Chris Lilley" <chris@w3.org<mailto:chris@w3.org>> wrote:


Hi folks,

It was recently pointed out[0] that the XYZ values for the D50 illuminant given on, for example, Matlab[1] or Bruce Lindbloom's site[2]

[0.96422, 1.00000, 0.82521]

differ from the once specified by the ICC

[0.9642, 1.0000, 0.8249]

"In ICC v4, the requirement was introduced that the media white point of a Display class profile shall be equal to D50 (i.e. [96.42, 100, 82.49])" [3].

I assume the authoritative source is the CIE. I will check my books this evening, but can anyone shed light on the discrepancy (and the correct value)?

[0] https://github.com/w3c/csswg-drafts/issues/2492#issuecomment-377913660<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fw3c%2Fcsswg-drafts%2Fissues%2F2492%23issuecomment-377913660&data=02%7C01%7Cborg%40adobe.com%7C170624fb6e4349eb71a508d598d73444%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C636582972420165772&sdata=b0Hx9oNM6U1I0jY%2BZ6mS30AEht0I5xwhYHIW04ePRHw%3D&reserved=0>
[1] https://www.mathworks.com/help/images/ref/whitepoint.html?s_tid=gn_loc_drop<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.mathworks.com%2Fhelp%2Fimages%2Fref%2Fwhitepoint.html%3Fs_tid%3Dgn_loc_drop&data=02%7C01%7Cborg%40adobe.com%7C170624fb6e4349eb71a508d598d73444%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C636582972420165772&sdata=UrKdFh9jiJR%2BZdhLzXvcaW0v7JQKC2EyvnJ%2BKPCUx1Y%3D&reserved=0>
[2] http://www.brucelindbloom.com/index.html?Eqn_ChromAdapt.html<https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.brucelindbloom.com%2Findex.html%3FEqn_ChromAdapt.html&data=02%7C01%7Cborg%40adobe.com%7C170624fb6e4349eb71a508d598d73444%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C636582972420165772&sdata=ISLiWta03%2BJIVj2EJc9HkxeYAI1PvztrpsE5Z9nvITA%3D&reserved=0>
[3] http://www.color.org/whyd50.xalter<https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.color.org%2Fwhyd50.xalter&data=02%7C01%7Cborg%40adobe.com%7C170624fb6e4349eb71a508d598d73444%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C636582972420165772&sdata=L7Nx%2Bif%2FVbStQ%2BfsCue4gmAsK%2BHijBvy3SgmLF%2BsMUE%3D&reserved=0>

--
Chris Lilley
@svgeesus
Technical Director @ W3C
W3C Strategy Team, Core Web Design
W3C Architecture & Technology Team, Core Web & Media