The problem of non-constant solid density is always there, it can be
minimised, however, by an adequate setting of the onset of the reciprocating
inking roller
and, if at all possible, by using a test forme with homogeneous ink demand
over the width of the forme.
If you care to measure tone value increase in more than one place along the
printing direction
you will be surprised
how much it can vary, so better take averages and do not expect precision
results.
Regards Mit freundl. Gru?en
Fred Dolezalek Dr. Friedr. Dolezalek
FOGRA, Graphic Techn. FOGRA Forschungsges.
Research Association Druck e.V.
dolezalek at
fogra.org
Tel. +49-89-43182-311, Fax +49-89-43182-100
PO. Box 80 04 69, D-81604 Muenchen, Germany
Streitfeldstr. 19, D-81673 Muenchen, Germany
-----Ursprungliche Nachricht-----
Von: eci-en-admin(a)lists.transmedia.de
[mailto:eci-en-admin@lists.transmedia.de]Im Auftrag von Yann Bouckaert
Gesendet: 27. August 2004 10:25
An: eci-en(a)lists.transmedia.de
Betreff: [ECI-EN] Re: Fastest way to find densities for ISO 12647-2
implementation?
Hello,
Thanks for answers regarding finding the appropriate density. The
density wedge is the way to go it seems. Another question comes to my
mind: would you put process colour step wedges on the same sheet to
determine the dotgain, or in a next printing run with the same density
across the width of the sheet?
I'm asking this, because when you take the route of the density wedge
to find the appropriate density, you must put the step wedges in one
row, perpendicular to the density wedge. Say you find that zone 14 has
the best density for cyan, you then look in that particular zone for
the cyan step wedge to determine the corresponding dotgain.
But: density can vary across the sheet in the printing direction. You
risk writing down dotgain results for an area that does not have the
same density as at the bottom of the page. I recently measured M 1.54
at the bottom of a page, M 1.44 in the middle op the page where the
step wedge was, and 1.54 again at the top. Dotgain for M at the bottom
was 19%, and 17% in the middle. No big deal maybe? I realise that after
putting appropriate correction curves in the rip to compensate for
extra dotgain, a new print run is needed to verify the results.
Sorry to bother you with all this, but practical advice is hard to find.
Have a nice weekend,
Yann Bouckaert
Sagam NV
Drongen, Belgium
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