Re: U.S. Web Coated (SWOP) v2 always produces blues that
Re: U.S. Web Coated (SWOP) v2 always produces blues that
- Subject: Re: U.S. Web Coated (SWOP) v2 always produces blues that
- From: Graeme Gill <email@hidden>
- Date: Mon, 09 Jul 2007 11:29:56 +1000
Harold Boll wrote:
It turns out there is more than one type of sRGB profile out there.
Hmm. I have what I thought is the original and only (ICCV2) sRGB profile,
the one from the sRGB web site setup by HP and Microsoft,
and the one that came with the extensive explanation of
how it was constructed. It has a date in the ICC header of
9 Feb 1998, 6:49:00, "Copyright (c) 1998 Hewlett-Packard Company",
"sRGB IEC61966-2.1".
Interpreting the profile correctly (ie. with the correct "right Von Kries"
white point transform) I get an absolute blue value using (my) icclib of:
XYZ 18.0511 7.2193 95.0770
D50 L*a*b* 32.300974 77.838457 -126.416983
Yxy 7.2193 0.149992 0.059987
The IEC sRGB standard says thaht the xy of the blue shall be
0.15 and 0.06, so the profile seems to be in alignment with the
standard.
The relative colorimetric blue I get is:
D50 L*a*b* 29.565320 68.301300 -112.049899
I was unaware that HP was muddying the waters by creating
a variety of sRGB profiles !
The demise of the sRGB web site hasn't helped in keeping track
of this either.
The above 3 profiles yield the following Lab values for RGB = [001] inputs:
(note: RGB range below is from 0-1 whereas in PS it is 0-255)
RGB = [0 0 1]
L* a* b*
32.3 62.5 -107.4 withBPC
29.6 68.3 -112.0 noBPC
29.6 68.3 -112.0 photoShop
Graeme Gill.
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