Re: ISO 12647-7
Re: ISO 12647-7
- Subject: Re: ISO 12647-7
- From: <email@hidden>
- Date: Wed, 23 May 2007 08:48:35 -0400
Hello,
The formulas are all related, using only different
variables. In particular, in the equation you give (inside
the square root):
da^2+db^2
is equal to
dE^2-dL^2
so
da^2+db^2-dC^2
is
dE^2-dL^2-dC^2
which is the same as
square(Delta-E*)- square(Delta-L*) - square(Delta-C*)
which was given previously.
For more formulas, have a look at the
Technical data/Definitions and theory/DeltaE
section of this document:
http://www.babelcolor.com/download/BabelColor_CT&A_Help.pdf
Danny Pascale
email@hidden
www.BabelColor.com
On Wed, 23 May 2007 09:56:03 +0400
"Gribunin" <email@hidden> wrote:
Hello!
I tried all formulas posted here in this list but all of
them seems to be
wrong. I'm comparing the result of formulas with the
result of CGS ORIS
Certified Proof calculation.
The only one formula which gave me zero difference
comparing to ORIS
Certified Proof results on all patches (I used
Ugra/Fogra MW2 scale) is dH
from http://www.brucelindbloom.com/, from Delta E94 or
dECMC calculation
steps.
The formula is the following:
dH = sqrt(da^2+db^2-dC^2)
Where dC=C1-C2;
C1=sqrt(a1^2+b1^2);
C2=sqrt(a2^2+b2^2);
Best regards,
Alexey Gribunin, UNIT Color Technologies,
Moscow, Russia.
Delta-H* is the contribution of the hue difference to
the
total error. It is obtained by removing the
contributions
of Delta-C* and Delta-L* from Delta-E*:
Delta-H* = sqrt( square(Delta-E*)- square(Delta-L*) -
square(Delta-C*))
As you noted, the angular difference will vary
significantly for neutral tones, but Delta-H*
will/should
not.
I do not have ISO 12647-2 i front of me but they are
most
likely talking of Delta-H*, not Delta-h*.
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