Re: U.S. Web Coated (SWOP)v2 vs. SWOP2006_Coated5v2
Re: U.S. Web Coated (SWOP)v2 vs. SWOP2006_Coated5v2
- Subject: Re: U.S. Web Coated (SWOP)v2 vs. SWOP2006_Coated5v2
- From: email@hidden
- Date: Mon, 7 Jan 2008 13:29:50 -0500
Todd Shirley <email@hidden> writes
on Fri, 4 Jan 2008 19:11:23
> This is more a "topic for discussion"...
Thanks to the many contributors of this thread; I've found it quite
informative. And since its being discussed I thought I'd weigh in on some
technical aspects of the 2 profiles in question.
QUANTITATIVE OBSERVATIONS:
Total Area Coverage (TAC)
USWeb 298%
SWOP2006 300%
Black Start (units %Cyan)
USWeb 40%
SWOP2006 35%
Max Black on Neutral Axis (Relative Colorimetric Xform)
USWeb 90%
SWOP2006 100%
K value @ L*= 50 (Rel Col)
USWeb 13%
SWOP2006 20%
Kvalue @ L*= 20 (Rel Col)
USWeb 80%
SWOP2006 80%
Black Pointt inking/color (darkest color on neutral; Rel Col)
USWeb CMYK = [73 68 68 89] Lab = [16.5 0 0]
SWOP2006 CMYK = [71 64 67 100] Lab = [13.2 0 0]
Round Trip A2B1/B2A1 (Methodology ensures all tested colors are inside
effective gamut)
Mean StnDev max-dEab
USWeb 0.746 0.461 2.57
SWOP2006 0.501 0.526 3.38
In his initial email Todd reports on differences in Lab for a given inking
between the 2 profiles. Unfortunately he probably utilized the A2B0 Xform
(perceptual) and interpreted it as being colorimetric which it is NOT.
Let's examine one of his inkings:
CMYK = [58,57,63,90] through A2B1 (Rel Col)
USWeb: Lab ~= [18.4 0.7 1.8]
SWOP2006 Lab ~= [18.1 1.3 1.2]
Now same inking through A2B0 (Perceptual)
USWeb: Lab ~= [7.7 2.2 2.4]
SWOP2006 Lab ~= [3.9 1.5 3.6]
The A2B1 Lab values ARE colorimetric and are essentially equal between the
2 profiles. The significance of the A2B0 (Perceptual) Lab values is that
they Round Trip with their B2A0 inking counterparts, thereby adhering to
the ICC spec. The point being is they hold no rigorous colorimetric
significance.
USWeb
ID: a* b* L* Chroma Inking
cyn: -41.39 -48.34 63.61 | 63.64 | 1 0 0
blu: 19.99 -48.36 30.92 | 52.33 | 1 1 0
mag: 76.14 -6.56 53.95 | 76.42 | 0 1 0
red: 69.81 45.20 53.60 | 83.16 | 0 1 1
yel: -6.30 90.35 95.08 | 90.57 | 0 0 1
grn: -67.54 27.13 58.88 | 72.79 | 1 0 1
SWOP2006
ID: a* b* L* Chroma Inking
cyn: -41.53 -48.97 63.61 | 64.21 | 1 0 0
blu: 20.30 -48.87 30.65 | 52.92 | 1 1 0
mag: 76.54 -6.74 53.81 | 76.83 | 0 1 0
red: 70.42 45.06 53.58 | 83.60 | 0 1 1
yel: -6.36 90.27 95.31 | 90.49 | 0 0 1
grn: -67.25 26.96 58.89 | 72.45 | 1 0 1
QUALITATIVE OBSERVATIONS
* Rel Col Neutral inkings for USWEB profile are monotonically increasing
from paper white to black pt. SWOP2006 shows a pronounced reversal in the
all the chromatic inks maxing out at ~19 L* down to B.P. at 13 L* (C:
75%->70%; M: 68%->64%; Y: 70%->66%). Reversal evident for Perceptual
Xform as well.
* CMYK separations for both profiles are quite good. SWOP2006
exceptionally smooth and free of any banding artifacts. USWeb pumps in more
K in deep shadows. (Rel Col)
* Attainment of most chromatic colors around cusp of gamut: USweb cleanly
hits the most chromatic colors which means that primaries & secondaries hit
their max values with no K present. SWOP2006 does well except for blue
where a significant amount of K is evident.
* The sRGB ink ramps from paper white to Blue are very similar and appear
to account for the 'blue-going-purple' problem in that Cyan >= Magenta.
* I wouldn't place much significance in the fact that the gridding for the
A2Bx xforms differ between the 2 profiles (USweb 9^3; SWOP2006 17^3). This
data is quite well behaved and doesn't require ultra-high sampling to be
characterized in the forward direction (ink to color). Note the good Round
Trip stats above for both profiles.
Harold
TOSHIBA AMERICA BUSINESS SOLUTIONS 2 Musick, Irvine, CA 92618
Harold Boll | email@hidden
" The sunlights differ, but there is only one darkness. "
Ursula K. Leguin
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