RE: [ECI-EN] Adobe and the Fogra ISO profiles
Bestmann, Guenter RD-PN32
5 Jul
2005
5 Jul
'05
9:09 a.m.
Hello,
Bob Marchant wrote:
"Our observations and trials of the ECI profiles agree very much with the views
above. We also have some issues with the ECI profiles when used with relative colorimetric
rendering intent (I'm not sure if these profiles were generated with this intent in
mind)."
According to the ICC Profile Format Specification (now also ISO 15076-1:2005) the content
of the relative (and absolute) colorimetric rendering intent should be the measurement
data without any modifications. The standard ECI profiles are build with this intent in
mind. The AtoB1 tag (CMYK to LAB) reflects exactly the measurement data. The BtoA1 tag
(LAB to CMYK) is the inverse of the AtoB1 tag with clipping of all LAB values outside the
color gamut of the printing process. The black generation is equivalent to the separation
tag.
Because of the very different goals in perceptual and relative rendering the results of a
color conversion are different.
Kind regards,
Guenter Bestmann
-----Original Message-----
From: Bob Marchant [mailto:bobphoto@dircon.co.uk]
Sent: Monday, July 04, 2005 5:01 PM
To: eci-en(a)lists.transmedia.de
Cc: "Florian Süßl"; Bestmann, Guenter RD-PN32; "Olaf Drümmer";
eci(a)lists.transmedia.de; Peter Constable; "Olaf Drümmer"
Subject: Re: [ECI-EN] Adobe and the Fogra ISO profiles
Hello all,
1 - Adobe gamut mapping is very smooth. During testing
of non-Adobe
profiles, we noticed some poor smoothness of perceptual mapping in
certain areas of the color gamut.
2 - Perceptual gamut mapping of Adobe profiles are consistent with
gamut mapping of many commonly used press profiling applications. This
leads to better consistency in workflows. We noticed that the ECI
profiles' perceptual mapping was significantly different than the
perceptual mapping of our current set of profiles (lighter in the
mid-tones).
Question: Is this a preferred perceptual mapping in the EU compared to
the Gretag/Adobe type rendering?.
3 - User's are aware of Adobe's gamut mapping strategies (they're in
our other profiles). The new (Adobe) Europe FOGRA27 profile shares
these traits reducing unexpected surprises when separations are
reviewed.
4 - We are not required to license Heidelberg's IP to distribute the
profile.
5 - ECI's profile creates a very long black starting at 0%. We have
been told that users like to see "cleaner" highlight color without K.
Our black starts at 30% of total ink.
Our observations and trials of the ECI profiles agree very much with the views
above. We also have some issues with the ECI profiles when used with relative
colorimetric rendering intent (I'm not sure if these profiles were generated with
this intent in mind).
We've been using both the new Adobe Europe FOGRA27 profile , and generating our own
profiles using the FOGRA characterisation data and Gretag software using varying
parameters for black generation depending on the images being converted/separated . Both
of these routes are working well, especially when using the relative rendering intent as
our work is for the best part totally colour critical.
As a matter of interest, are Adobe considering building profiles with varying amounts of
GCR/UCR for use on an image by image basis? (On a recent project we produced a
'family' of profiles for a photographic publishing project. Just three were needed
to deal with the various types of images reproduced in the book concerned).
As far as licensing of profiles is concerned, we understand that there may still be some
issues. This has been much discussed among the various standards committees we are
involved with. Initial contact with some of the profiling software/ hardware companies
points to some leeway in this area for profiles placed in the public domain , but this has
yet to be confirmed.
Bob Marchant.
Bob Marchant Photography / Colour Therapy