AM/FM screens
AM/FM screens
- Subject: AM/FM screens
- From: Dan Wilson <email@hidden>
- Date: Mon, 16 Jun 2008 21:26:06 +0100
- Thread-topic: AM/FM screens
Hi List/Lee,
I don't know which G7 people you have been talking to, but the Solid Ink
Density G7 targets is the same as that which you target in a TVI
calibration.
I cannot think of any reason to change from target density if you are
producing an ISO quality product.
Maybe you need to look over the "G7 How To" from www.gracol.org again to
update and really understand the process.
Using FM plates exposed on the same calibration curve used to expose AM
plates will not work. Simply reducing the density would not achieve anything
near a desirable result using either TVI or NPDC (Near Neutral Print Density
Curve). It would probably be solid from 60% up.
You need to have one calibration set for AM and a different calibration set
for FM printing.
Google up 'John Lind' and 'GATF'. Some years ago John did an excellent
research project on web presses running conventional and stochastic
screening. He documents reduced in usage, the $ gains and explains the
reasons.
Another handy explanation of stochastic and ink usage that I like can be
found at:
http://www.bsink.com/tech/StochasticScreening.pdf
Hope this helps clear some confusion - or am I just adding a sort of
stochastic "edge interference" to the discussion.
Regards,
Dan Wilson
Managing Director
--
G7 Certified Expert
UGRA Certified Expert/Consultant
--
Prepress I.T. Limited
Dublin, Ireland
Dublin +353 (0)85768 2733
www.prepress-it.com
> ------------------------------
>
> Message: 10
> Date: Mon, 16 Jun 2008 10:48:08 -0700
> From: Steve Upton <email@hidden>
> Subject: Re: Colorsync-users Digest, Vol 5, Issue 209 - AM/FM screens
> To: ColorSync <email@hidden>
> Message-ID: <p0624080ac47c56b1e49d@[216.254.4.110]>
> Content-Type: text/plain; charset="us-ascii"
>
> At 9:38 AM +0100 6/16/08, Lee Badham wrote:
>> Hi List,
>>
>> 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.
>>
>> 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.
>
> It seems to me that curving the system differently is what would reduce the
> dot gain (or perhaps more clearly, the tone curve characteristics) to match AM
> system behavior.
>
> While gray balance is very important, it seems that setting up the system
> correctly to anticipate the different tone characteristics of FM screening
> would be the first place to start.
>
> If a printer is trying to compensate for TVI differences using ink ducts alone
> then there is a bigger problem here no?
>
> It is certainly not the G7 way of doing things... or perhaps I'm confused by
> your statement.
>
> Regards,
>
> Steve
>
>
> ________________________________________________________________________
> o Steve Upton CHROMiX www.chromix.com
> o (hueman) 866.CHROMiX
> o email@hidden 206.985.6837
> ________________________________________________________________________
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