Re: [ECI-EN] Isocoated vs EuroscaleCoated vs. EuropeIsocoatedFogra27
7 Nov
2005
7 Nov
'05
10:23 a.m.
Hi Marttila,
you wrote:
Hello
Very interesting data - thank you. Yes I was using perceptual - with relcol
differencies are smaller and Isocoated/EuropeISocoatedFogra27 are much
closer to each other than Euroscale.
However I don't fully understand your second picture - to what do you
compare the Lab values to get Delta E94?
For the first picture I took a gray ramp in Lab (0/0/0 thru 100/0/0),
converted it to CMYK unsing the profiles and rendering intents specified
in the legend and then converted it back to Lab using the absolute
colorimetric intent of the particular profile.
The data for the second picture comes from Graeme Gills "profckeck"
utility, documentation can be found at
http://argyllcms.com/doc/profcheck.html
As Test point data file I used FOGRA27
(http://www.color.org/FOGRA27.html) converted to argylls ti3-Format.
Klaus
BR Jouni
-----Original Message-----
From: eci-en-admin(a)lists.transmedia.de
[mailto:eci-en-admin@lists.transmedia.de] On Behalf Of Klaus Karcher
Sent: 4. marraskuuta 2005 16:00
To: eci-en(a)lists.transmedia.de
Subject: Re: [ECI-EN] Isocoated vs EuroscaleCoated vs.
EuropeIsocoatedFogra27
Marttila Jouni wrote:
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Hello
I was just looking at some natural pictures with skintones etc..
E.g. the picture attached where woman is drinking. By calculating
pixel by pixel the avg Delta E between
ISOcoated and Euroscale = 4.36
ISOcoated and EuropeISocoatedFogra27 = 3.57
EuropeISocoatedFogra27 and
Euroscale = 1.12
So EuropeISOcoated is closer to Euroscale and main
difference seems to
come from luminance level, which is higher with
ISOcoated
than the two
others.
Are you talking about perceptual conversions from PCS to Device unsing
Adobe Euroscale Coated v2, Adobe EuropeISocoatedFogra27, and
eci ISOcoated?
As I mentioned in January in the German list, the B2A0-Tables of
PrintOpen Profiles (as used by the eci) induce this luminance
displacement.
see:
http://digitalproof.info/perceptual-rendering/DeltaL.pdf
* euCo2 means "Adobe Euroscale Coated v2"
* isoC means ECI ISO Coated (PrintOpen)
* IsoC-G3-350-CF is a ProfileMaker5 Profil
and relTK means "relative colorimetric with blackpoint compensation"
eci ISO Coated's perceptual rendering is significant lighter than that
of most other profiles and IMHO this shold be corrected in
further versions.
On the other Hand, both Adobe profiles (Euroscale Coated v2 and
EuropeISOcoatedFogra27) are imho not suitable for proofing
tasks (using
its colorimetric Tables), because the error produced already by the
profiles (not by the proofing system!) makes it realy
difficult to meet
the close tolerances for proofing, as you can see in
http://digitalproof.info/profcheck/profcheck5ir1b1.html
regards, Klaus
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