The LCMS2 API gives x=0.3127, y=0.3291 as the D65 source white point values to use when making an sRGB profile.
These two references quote *two* sets of xy values right on the same page, in two different tables, each time saying the values are the CIE values for D65: http://www.w3.org/Graphics/Color/sRGB http://www.color.org/sRGB.xalter From Table 0.1 and notes: Illuminant White x = 0.3127, y = 0.3291 (D65) The chromaticities of the illuminant white are those of CIE D65. Farther down the page, Table 0.2: The CIE chromaticities for the red, green, and blueITU-R BT.709 reference primaries, and for CIE Standard Illuminant D65, are given in Table 0.2 [which says] D65 x 0.3127 y 0.3290 sRGB is supposed to be compatible with Rec709. Poynton gives x=0.3127 y=0.3290 as the right values for D65. (http://www.poynton.com/PDFs/ColorFAQ.pdf, Q17). This page: http://www2.units.it/ipl/students_area/imm2/files/Colore1/sRGB.pdf gives x = 0.3127, y = 0.3290. This page from the wayback machine's archive of the original sRGB color space website: http://web.archive.org/web/20030212204955/http://www.srgb.com/basicsofsrgb.htm gives x = 0.3127, y = 0.3290. The AdobeRGB specifications give x = 0.3127, y = 0.3290. As AdobeRGB reputedly was derived by accident from sRGB by modifying the green primary, it seems like they ought to use the same source white point values. The ICC spec version 4 gives X=0.9505 Y=1 Z=1.0890, which when converted to xyY is x=0.31271591, y=0.32900148, which rounded to 4 decimal places is x=0.3127, y=0.3290 Changing the source white point values does change the resulting profile. All the references give x=0.3127, y=0.3290 as either "the" value or as one of two sets of values. Why do some references give that second set of values? Is there a reason to prefer x=0.3127, y=0.3291 to the more commonly quoted x=0.3127, y=0.3290? Regards, Elle ------------------------------------------------------------------------------ Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121051231&iu=/4140/ostg.clktrk _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
