Re: Colorsync-users Digest, Vol 5, Issue 209 - AM/FM screens
Re: Colorsync-users Digest, Vol 5, Issue 209 - AM/FM screens
- Subject: Re: Colorsync-users Digest, Vol 5, Issue 209 - AM/FM screens
- From: Mike Eddington <email@hidden>
- Date: Mon, 16 Jun 2008 10:09:40 -0400
>FM screening has a higher dot gain than conventional screens. This
is because of there are many smaller dots, each which can spread (more
circumference), rather than a lesser number larger dots
This phenomenon wouldn't necessarily be limited to FM screening.
Higher LPI conventional screening would see a similar effect (though
perhaps not as profound)...a need to reduce the plate curve to meet
the same tonality as lower LPI printing. FM screening's distribution
of dots generally allows more light to be filtered by the ink (as well
as increased filtering the effects of the substrate), which could
account for more efficiency from the ink, as well as slight
differences gamut/hue compared to traditional LPI/screening.
>So what the printer is doing is closing the ink ducts and reducing
the solid ink density to reduce the dot gain back to the same as that
of the AM screened plates. That surely will also affect the solid ink
colours. Maybe because it won't affect the grey balance, the G7 people
think this is ok. The solid colours are not affected by the screening
technology used, because there is no screen.
Roger's description of closing the ink ducts does illustrate the point
of less required ink consumption for FM screening (below 100% coverage
anyway), but this would not be the appropriate method of reducing TVI/
tonality as it would affect the solids (as stated). More appropriate
would be curve compensation at the plating stage (or device-links).
Its a bit inaccurate to say that G7 people would think it ok to reduce
SID to hit the desired TVI, after all, solid Lab and tonality are a
large part of the G7 process, not just gray balance.
One more general comment, though ink consumption may be lower overall
for FM screening, the tighter window needed for process control, and
other potential issues, such as piling, that may raise their head, may
work to reduce any overall savings from ink consumption alone. Its a
bit more than just switching the screening at the Rip.
Michael Eddington
QA Manager/G7 Certified Expert
North American Color, Inc.
www.nac-mi.com
www.nac1to1.com
www.photo360.com
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