Re: [ECI-EN] RGB to CMYK
by Mike Eddington
I agree that problems such as this might not be clearly evident in the
final prints, as the crux of this issue occurs at the separation
stage. The press can be reproducing the CMYK values superlatively
toward Fogra39 and/or the proof, but they may not be the same CMYK
values we might have had using a different profile for separation
(i.e. different gamut mapping), and any issues of undesirable
purplish-blues due to the separations may have been corrected by press
time. I'll also agree that the purplish-blue issue is most apparent
for extremely out of gamut blues, but can be witnessed in converting
real world RGB images as well. I don't wish to blow this issue out of
proportion however. Suffice to say that gamut mapping is subjective,
and the end user would do well to analyze a profile prior to
incorporating it into a workflow to ensure it meets their needs.
Michael Eddington
QA Manager/G7 Certified Expert
North American Color, Inc.
www.nac-mi.com
www.nac1to1.com
www.photo360.com
> ------------------------------
>
> Message: 5
> Date: Tue, 5 Feb 2008 09:04:50 +0100
> From: "Bestmann, Guenter RD-PT23" <Guenter.Bestmann(a)heidelberg.com>
> Subject: Re: [ECI-EN] RGB to CMYK
> To: <eci-en(a)lists.callassoftware.com>
> Message-ID:
> <E30A95A7B013094997CABEC3F488573CFF8637(a)wiems02014.ceu.corp.heidelberg.com
> >
>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Dear all,
>
> the profile ISOcoated_v2_eci was build with Heidelberg's PrintOpen
> 5.2. Before publishing the profile a lot of tests were made. ECI
> made also some comparisons with profiles from other vendors. The
> final decision was for the PrintOpen profile because from an overall
> point of view this profile has some more advantages than
> disadvantages with respect to other profiles.
>
> I will not discuss the advantages and disadvantages with respect to
> profiles of other vendors.
>
> In normal circumstances you will not find any problems when printing
> with this profile. Problems may (but must not) arise when separating
> extremely out of gamut RGB-colors, for example an AdobeRGB blue with
> RGB = 0/0/255. Mapping of extremely out of gamut colors in this area
> may cause a (slightly) purplish blue. In addition to the gamut
> mapping this purplish blue depends on the ink trapping too.
>
> I never saw printed samples which are not useable or sellable when
> a) printing to the ISO standards colorant values and tvi curves and
> when b) preparing and separating carefully images or graphics before
> printing.
>
> The rumors about quality problems with ISOcoated_v2_eci and other
> ECI profiles are from other profile vendors and from people looking
> only at separations and previews and not at the final prints.
>
> Heidelberg uses this profile together with other profiles build with
> PrintOpen in their show rooms and education centers. If there are
> real problems with the separations then we were the first to solve
> these problems. The purplish blue for extremely out of gamut colors
> was corrected in the new version of PrintOpen available soon.
>
> Kind regards,
> Guenter Bestmann
>
>
> Dr. Guenter Bestmann
> Research & Development
>
> Heidelberger Druckmaschinen AG
> Dr.-Hell-Strasse
> D-24107 Kiel
> E-Mail: guenter.bestmann(a)heidelberg.com
> Tel: +49-431-3863887
> Fax: +49-431-3863287
16 years, 3 months
- 1
- 0
RGB to CMYK
by bruno Voidey
Hello
I'm working as free lance in France, i've got a scitex scan and an
Epson 4800 with a best Designer for printer.
I work as long as possible in RGB and i convert at the end in CMYK, i
used euroscale coated and changed for isocoated ECI 2 years ago and
it seemed to be better.
But today i've heard that the isocoated and new isocoated V2 wasn't a
good profil for converted my RGB imaged (working space eci RGB V2) in
CMYK ? and that it's just a profil of "simulation" for the printer !
Is it true ? and should i use a profil like the new isocoated
frogra39 for the coated paper i use generaly.
I've made a lot of test and print a lot of book without any problem
with a lot of printer, i was estonished.
Can you help me ?
sinceraly, bruno
16 years, 3 months
- 4
- 3