Talk:Illuminant D65

Subscript?
I finally found it in amazon's search; the Schanda ref obviously just made an error in typesetting a table, as that's the only place where D65 is written with subscripted 65. So let's leave it out, OK? Dicklyon (talk) 05:31, 17 April 2008 (UTC)

...but it's not the only place. In Chapter 2, page 17 you can find:

Perhaps, though, the CIE should have heeded Guild’s warning when the new daylight distribution D65 was defined in 1964 by its spectral power distribution. When samples which ﬂuoresce have to be measured, we often need a laboratory source which simulates D65, but none is available which exactly reproduces its spectral distribution. It might have been better to have developed a source that simulated the D65 distribution closely enough for most practical purposes and to have adopted that source as the standard, with its energy distribution being given as a supplement to the definition.

Looking at other authors: "…CIE Standard Illuminant D65…, "The CIE D illuminants are properly denoted with a two-digit subscript."

--Adoniscik(t, c) 15:14, 17 April 2008 (UTC)


 * I’ve been reading through a bunch of color science papers, and as far as I can tell, using the subscript is the standard notation (as well as sometimes italicized capital letters for illuminants). Is there a source which recommends the "D65" notation, or is that just an artifact of writing (e.g. on typewriters) where subscripts are difficult to achieve? (I don’t have easy access to the CIE specifications themselves; if anyone does, and would write in, that would be great.) –jacobolus (t) 16:12, 10 May 2010 (UTC)


 * Books that use a subscript (sitting in a university library, so they were handy :): Agoston’s 1979/1987 Color Theory and its Application in Art and Design (part of a series edited by MacAdam), Wyszecki & Stiles’s 1982 Color Science. Billmeyer & Saltzman’s 1966 Principles of Color Technology refers to the “proposed illuminant D6500” (which had apparently not yet quite been ratified by the CIE after its recommendation by one committee, based on Judd’s work). Gerritsen’s Theory and Practice of Color just refers to “standard D”. Fairchild’s 2002 Color Appearance Models uses the “D65”, etc. nomenclature. –jacobolus (t) 19:10, 13 May 2010 (UTC)


 * Yes it would be best to find an authoritative source like a CIE standard. Based on my perusal of books on Google Book Search, though, I'd say the overwhelmingly most common way is NOT subscripted, especially in the expression "CIE illuminant D65".  Dicklyon (talk) 23:04, 13 May 2010 (UTC)

XYZ values of D65
It is written that «Normalizing for relative luminance, the XYZ tristimulus values are X=95.04, Y=100.00, Z=108.88». But, according to http://en.wikipedia.org/wiki/CIE_1931_color_space, (x,y), given the brightness Y, are converted to XYZ as follows: X=Y/y*x, Z=Y/y*(1-x-y).

Using these formulas, we will get for Y=100.0:

X=100.0/32902*0.31271=95.04285...,

Y=100.0,

Z=100./0.32902*(1-0.31271-0.32902)=108.890037...

So, I think it is better to round Z as 108.89, not 108.88 as stated in article.

217.67.117.64 (talk) 09:27, 11 December 2008 (UTC)


 * I think it is better to use published figures. I was able to find 108.88 in my books; e.g. pg.247 of Color Appearance Models by Fairchild. (Note that the cited x,y,z values are rounded off.) --Adoniscik(t, c) 18:50, 11 December 2008 (UTC)


 * You could compute the X, Y, Z by taking the dot product of D65 with the x(λ), y(λ), z(λ) of the 1931 standard observer, if you want. –jacobolus (t) 16:20, 10 May 2010 (UTC)


 * Five years later... O.K., I did that. I used the 1nm data set from . Result: x=0.312727, y=0.329023 and X=95.0471, Z=108.883. It looks like x in the article is off in the last decimal place. Hussell (talk) 00:53, 8 March 2016 (UTC)
 * There has been discussion on this topic here: Talk:Standard illuminant
 * tl;dr: The figures currently listed in this article (0.31271 and 0.32902) are wrong. The correct values are 0.31272 and 0,32913. — Preceding unsigned comment added by 77.61.180.106 (talk) 15:11, 3 January 2021 (UTC)

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Removed Chromaticity %Values
I removed the edit by user @Crissov where chromaticity coordinates were expressed as % values, in addition I also verified the chromaticity values using the XYZ values stated on the article. Chromaticity coordinates are not a scaler color space, there is no relative meaning between 0 and 1. While it is true that in the 2-degree chromaticity space, the values do add up to 1 this is not true for other chromaticity spaces. It's merely a small mathematical artifact from other design decisions for the 1931 std. obs. TDcolor (talk) 17:10, 26 April 2023 (UTC)


 * What do you mean don't add up to 1? $$z = 1 - x - y$$ by definition ($$x = X / (X + Y + Z)$$ etc.) –jacobolus (t) 17:38, 26 April 2023 (UTC)