Re: ISO 12647-7
Re: ISO 12647-7
- Subject: Re: ISO 12647-7
- From: Rolf Gierling <email@hidden>
- Date: Wed, 23 May 2007 11:33:11 +0200
Hello List, hello Gribunin,
Dannys formula is correct, and the one is used by the fogra too.
To summarize:
dH = sqrt ( dE^2 - dL^2 - dC^2 ) or:
dH = sqrt ( da^2 + db^2 - dC^2 ) which is the same
where
dC = C1 - C2
C1 = sqrt ( a1^2 + b1^2 )
C2 = sqrt ( a2^2 + b2^2 )
Rolf Gierling
Am 23.05.2007 um 07:56 schrieb Gribunin:
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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