Re: Out Of Press Gamut (rewrite)
Re: Out Of Press Gamut (rewrite)
- Subject: Re: Out Of Press Gamut (rewrite)
- From: Roger Breton <email@hidden>
- Date: Sat, 24 Dec 2005 12:20:29 -0500
Roberto and Bill,
> Is it possible that you don't have a correct flexo linearization? From
> what I've known normalizing the dot gain in flexo presses is tricky,
> and usually involves multiple iterations at curve building (like
> Barco's Intellicurve for example).
Let alone having any flexo linearization. Bill did not say how he produces
his photopolymer plates, from films or direct digital.
> It could be that the dot gain in highlights (as your M=7% for example)
> is behaving in a way that the profiling software, with a limited
> sampling, can not accurately predict.
If Bill said he used the ECI2002 target, there are precisely 7% patches in
all four process colors so I don't see that being the issue.
> I understand that IT8/7.4 was created as a superset of ECI2002
> precisely to add some patches that flexo people deemed necessary.
> Maybe you should use it.
The extra patches the IT8/7.4 has are 10% of black in combination with a
number of CMY builds. To me, what flexo really needs is more combination of
2% and 3% and 4% and 5% patch to better catch the dot behavior in that
critical part of the tone scale. I gather that the 10% black introduction
was to satisfy the "packaging" requirement: maybe they meant "offset"
packaging as opposed to "flexo" packaging?
> Nevertheless, your 'color out of press gamut' problem seems to run
> deeper. Two other factors come to mind:
> 1) maybe you're printing flexo on plastic? maybe very glossy or pearl?
You mean like 7 mill white plastic?
> in that case, a polarization filter (unfortunately not available in
> DTP-41, only in Spectrolino) could cut on the effect of gloss.
OK.
> 2) presence of optical brighteners on the substrate (the flexo print
> substrate).
Makes sense.
> While building the profile the software would be
> compensating for them, but when measuring the sample alone it
> wouldn't.
Aren't optical brighteners fun?
> Try disconnecting the compensation from the software to see
> what difference it makes in the resulting profile.
OK.
> Oh, I am assuming when you say "I measured this color" (below) you
> mean from the press sheet.
That's where I'm confused. Because the rest of my reasoning hings on that
very assumption.
> (since you say this challenge does not
> include the Epson). Am I right? make sure you are measuring it in
> absolute Lab mode, in case your software allows for different
> measuring modes (as for example relative to the substrate).
>
> -- Roberto Michelena
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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