Re: Inkjet Ink restrictions
Re: Inkjet Ink restrictions
- Subject: Re: Inkjet Ink restrictions
- From: Scott Martin <email@hidden>
- Date: Mon, 2 Jun 2008 16:54:35 -0500
On Jun 2, 2008, at 6:25 AM, Mark Rice wrote:
The RIP
manufacturers, strangely, seem to have no interest in resolving this
"art"
of creating initial ink restrictions as the base for creating a
profile.
It's all done by eyeball, with predictably unpredictable results.
I was impressed a number of years ago when the Bestcolor Color Manager
started graphing bird's eye hue lines for the solid colors. From this
graph you could visually see the hue hooks that occur when ink
densities get excessive. Best Color Manager suggested placing ink
limits at the base of each hook for offset proofing and a ways into
the hook for fine art printing. I appreciated the science and
visualization of that process.
I would like to see a method of generating initial ink restrictions
based on
density values and some form of gray balance throughout the
linearization
range.
For this we might look at ColorBurst's process for ink limiting. Their
process involves studying chroma values and placing the ink limiting
where chroma stops increasing. This chroma process proved to be a nice
improvement over watching density values alone. After the inks limits
are set, proceed with Lab based grey balance linearization...
Different inksets require different approaches though. Pigment and UV
curable inks maintain a pretty high TAC when the per ink limiting is
high. Solvent inks, however, often require the user to maintain a
lower per ink limit so that the TAC doesn't fall too low and sacrifice
shadow saturation.
We could talk about how a few other RIPs address ink limiting but I
think it's safe to say that its not totally an art (or a craft). There
are some good rules of thumb which are known to produce fantastic and
repeatable results. I'd certainly agree that RIPs could be smarter
about making it more intuitive for the new user.
In the photographic world of the Lambda and Lightjet, Fuji and Kodak
publish
aim point densities for their different photographic materials.
Unfortunately with all the different software applications and devices
managing the linearization of these devices we rarely see results as
consistent as we need for B&W printing across a group of these RGB
devices. Take any lab with combinations of Durst, OCE, ZBE, Noritsu,
Agfa, Fuji and Kodak silver halide printers and you'll see notable
differences on the same paper even with fresh calibrations. This is a
good example of where the theory and real world practice don't line
up. The only solution seems to be profiling all of them with a single,
external solution that controls grey balance.
Scott Martin
www.on-sight.com
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