Hello,
One of my friends who happen to be ISO auditor, told me that ISO does not mean a thing,
with ISO you can manufacture concrete parachutes; The only thing you can be sure with this
parachute (except that it will be really heavy and you will be surely killed if you use it
:) is that first one and last one will be the same and manufacured against manufacturers
specification.
So, probably the same thing applies to ink manufacturers. They might be ISO9001 certified
but that does not mean that their manufacturing process complies with other ISO standards
regarding very ink they manufacture.
Now when you mention proofers, one of the things missing in ISO is definition of
acceptable color proof, I understand that proofing as such is not within scope of
iso12647-2 as such, but there should be a guideline about what should be acceptable. We
currently try to use definition of variation tolerance from our in-shop standard against
proofer. Unfortunately this definition is too strict. In my experience at least some of
the colors will be way off the chart (deltaE of 7-8 on the proof), but I think that
methodology used in GATF or Stuttgart shootout was pretty good, so you can say that (for
example) acceptable proof is any proof with average deltaE of 4 or less and with maximum
deltaE of ie. 8 - experiment shows that this far away colors are usually really dark
colors with heavy ink coverage and are hard to spot anyway.
There is also a issue with targets, I have downloaded eci2002 target and I understand the
idea behind it. I am not so sure that we could create one-size-fit-all target. Take for
example three scenarios (and the case you read each 10% from 0 to 100%);
- laser printer, this device is linear and will equally cover the whole area from 0 to
100%, and we can say that readings made from this target may accurately represent what
will happen on our device
- printing press, well, here we have dot gain (or TVI), when you read this chart, you will
see that difference between readings are for some areas are smaller, and for some values
you will have larger gaps
- inkjet proofer, same like offset press but really drastic, with this kind of target you
can not accurately map behaviour of inkjet proofer because large portions of tonal range
will not be measured at all
This also leads to grey balance problem, having reached ISO12647-2 lab targets for solids,
and applying correct correction curve to receive exemplary response on the machine you can
not be sure to have optimal grey balance because of wet trapping properties of the ink.
Depending on the dot shape used and overlaping of the dots you will have more or less area
overlaping and trapping will be different. This might not be so interesting in
conventional screens, but with FM I am 100% sure you can not reach grey balance with
ISO12647 settings (in FM dot gain does not follow a curve as in conventional screens but
it is something like S shaped).
---
I just found out that I'm one inch taller than I thought.
mailto:marko@printel.hr
http://printel.hr
-----Original Message-----
From: Vladimir Gajic [mailto:vgajic@abc-digital.com]
Sent: Friday, January 03, 2003 11:57 AM
To: eci(a)lists.transmedia.de
Subject: Re: RE: [Eci] Re: ISO 12647 / Ink deviation
Happy New Year everybody.
It´s really interesting to read this topic. Most of the German and European Printers could
learn from You...
A couple of Weeks ago we had a meeting with some people from Creo her in Hamburg. One of
the topics was the stability of Iris Inks. We asked them to issue a
quality protokol for each batch-number of Ink they manufacture, and I can asure You that
this will be a hard peace of work. Most of the ink - producers will not - due to political
reasons -issue reference values for their inks.
The problem with printing inks is quiet larger. Even if a manufacturer claims that his
product is ISO - certified it does not mean that this ink will match the needs of
the dayly process. Even the deltaE - Values specified within the ISO can not match these
tolerances. They are hard to match for the printing process, but far to
generous for most of the proofing systems today. By all means, if the values of Your
media-wedge match the ISO - specifikations that don´t mean that your proof or
print will show You the correct result. You have to rely on more precise tools like the
new ECI 2002 Charakterisation Target. Colorimetric measurement is in deed
the only possible way to go and the printers should start using it as soon as possible.
The standard was not written just for pre-press people but also for printers too.
Kind regards with the best wishes for your work
--
=======================================
Vladimir Gajic
Colormanagement
---------------------------------------
Albert Bauer KG
Conventstr. 1-3
22089 Hamburg
Phone: ++49 40 251 09 225
Fax: ++49 40 251 09 121
E-mail: mailto:vgajic@abc-digital.com
Homepage:
http://www.abc-digital.com =======================================