Hi Juris,
ISO 12647-1 states that a printing condition includes the specification of surface
finishing (varnish or laminated film).
Currently we do not have any reference printing conditions which include varnish or
lamination in ISO.
ISO 12647-1 also requires that additional CIELAB values must be specified for paper, solid
inks, and CM, CY, MY secondaries after finishing.
(I've never seen or heard of that done in practice.)
ISO 12647-2 only notes that surface finishing will change the final color appearance, and
later on suggests to use two proofs (before and after finishing) for critical jobs.
This implies that target values for surface finishing must be different. So there are no
ISO-standardized target values for any kind of surface finishing.
I agree with Jani that one generally should not varnish the print control strip. This
means printing to ISO standard and accept the changes due to surface finishing.
There are exceptions where a compensation is possible, mainly with glossy aqueous
dispersion varnish.
Depending on the matte-ness of your varnish it is not possible to reach the ISO aim values
for printing on coated paper with a stable printing process.
You will likely have too much stray light from the surface which limits gamut and depth.
E.g. your L* will be too high no matter how much solid black ink you are printing.
However, for glossy and matte lamination there is a new set of ICC profiles and target
values available on the ECI and Fogra web sites.
This does not directly apply to varnish, but a document is included that contains useful
information.
Of course, customers do not want to be bothered with this, they deliver a FOGRA39 proof
and leave the rest to you.
Education is necessary to make them see that compensation is not always possible, and make
them accept either the changes due to finishing, or to take finishing into account during
separation and proofing.
(It's easy to say this when there are no standards around for varnish. But if the
demand is high enough, we (ECI) might consider publishing more specialized data sets and
profiles.)
Best regards,
Hanno
Am 10.04.2012 um 11:19 schrieb Juris Valdmanis:
Hello Jani!
Thanks for your reply.
When coating is applied, AxisControl will try to get to ISO targets as close as possible
by opening/closing ink keys. The doubt are that there is too much of ink under coating and
printing so much ink makes process very unstable. Also dot gain becomes very high.
What does ISO says about coating? Does coated sheet should hit same targets as uncoated?
Even when coating makes inks less saturated?
What is your experience what do customers require?
regards,
Juris
From: Jani Vauhkonen - PunaMusta Oy <jani.vauhkonen(a)punamusta.com>
To: eci-en(a)lists.callassoftware.com
Date: 2012.04.03 14:37
Subject: [ECI-EN] Varnish desaturates
Sent by: eci-en-bounces(a)lists.callassoftware.com
Hello Juris.
I would suggest not print varnish on colorbar.
But if somebody has investicated different target values for printing CMYK+varnish, it
could be interesting to hear.
We have made some test.. If the desaturation could be compensated by increasing density,
color densities should be increased by 8-11%. It might cause invalid tvi values, and that
should be compensated in prepress.
After all, the final result is not the same if you increase density on varnish job vs
leaving the varnish away.
Matt varnish desaturates, and that is what it is for.
-----------------------------------------------
Kind regards:
Jani Vauhkonen
Prepress manager
PunaMusta Oy
PrePress division
P.O.Box 99, FIN-80141 Joensuu
Kosti Aaltosen tie 9, FIN-80140 Joensuu
Tel. +358 10 230 8481
jani.vauhkonen(a)punamusta.com
www.punamusta.com
-----------------------------------------------
--
Dr. Hanno Hoffstadt
Color Scientist
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