Re: delta E 2000 discrepancy
Re: delta E 2000 discrepancy
- Subject: Re: delta E 2000 discrepancy
- From: <email@hidden>
- Date: Tue, 27 Mar 2007 17:04:27 -0500
Mike,
I entered your values in a small text file:
L*;a*;b*
24,13;17,2;-46,14
24,48;17,17;-42,77
1st test:
I opened the text file with PatchTool and compared the
first patch with the second one, and got 1.78 (CIEDE2000
1:1:1) (Note: you can do this in PatchTool trial mode).
2nd test
From PatchTool, I exported the L*a*b* values in CGATS a
first time.
I switched the samples and saved again, as CGATS.
I then compared the two CGATS file in MeasureTool and
obtained the same 1.78 value (CIEDE2000).
Note: you can also do test 2 in PatchTool, only faster ;-)
As for 1.78 or 1.74, I can only say that PatchTool matches
MeasureTool numbers (not a proof in itself you could say)
but, more scientifically, I validated PatchTool CIEDE2000
formula with reference data sets proposed in an article by
one of the CIEDE2000 formula developer (which I do not
have at hand unfortunately).
Hope this helps,
Danny Pascale
email@hidden
www.BabelColor.com
On Tue, 27 Mar 2007 16:56:23 -0400
"Mike Eddington" <email@hidden> wrote:
Maybe someone can clear this up for me. I was checking a
spreadsheet
that calculates delta E 2000 for errors when I noticed a
discrepancy
between the values I derived, and those I got with the
Color Difference
Calculator at Bruce Lindbloom's website. I was getting a
delta E 2000
value of 0.8752155 while Bruce's calculator comes up
with dE 2000
1.744262. For fun I found two other sources...ColorThink
Pro, which
matched Bruce's value, and the
ColourDifferenceFormulas.xls file located
here > http://www.digitalcolour.org/Difference.htm,
which matches my
value. Many other values match between all, but I can't
figure out where
the discrepancy lies...the weighting factors are
identical. I might be
able to pin the issue, but ColorThink and Bruce's
calculator don't show
their work...and quite honestly, the delta E 2000
formula makes my head
hurt just looking at it. Here's the values in question
and values
derived from my spreadsheet and the
ColourDifferenceFormulas.xls :
Weightings
KL
1
KC
1
KH
1
Reference
L
24.13
a
17.20
b
-46.14
C
49.241645
a'
17.246573
b'
-46.14
C'
49.257932
h'
290.49513
Sample
Ls
24.48
as
17.17
bs
-42.77
Cs
46.087762
G
0.0027077
a's
17.216491
b's
-42.77
C's
46.105103
h's
291.92659
mean C'
47.681517
mean h'
291.21086
h
1.4314573
L
0.35
C
3.1528295
H
1.1905758
T
0.3631734
SL
1.3797167
SC
3.1456683
SH
1.2597499
19.702196
RC
1.9891956
RT
-1.262721
E00
0.8752155
Michael Eddington
North American Color, Inc.
www.nac-mi.com
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