ink resrtictions
ink resrtictions
- Subject: ink resrtictions
- From: David Wollmann <email@hidden>
- Date: Thu, 14 Dec 2000 16:19:44 -0700
- Organization: Luna Vista Imaging
I would like to get some opinions from the list members on how to
approach setting Ink Limits before the profiling of multi-ink devices
such as the ColorSpan Displaymaker 7100. This printer uses CMYK, Medium
Cyan, Light Cyan, Medium Magenta, and Light Magenta inks.
What I would most like to hear are techniques for determining Ink Limits
for multi-ink printers.
Having the correct levels set for these lighter shades is important
since the transition between them and the normal >dark< shades of ink
will affect the smoothness of gradients as well as how neutral they can
print a file that is grayscale. Also the overall gamut of a particular
ink and paper combination is greatly affected by Ink Limits.
Vinyls and canvas can be problematic when using pigmented inks. These
materials seem to need very high levels of ink limiting in order to
avoid bleeding, and as a result the gamut suffers. So, I want to find a
way of finding that elusive edge between over inking and reducing the
Ink Threshold more then necessary.
Is there any method that can remove the subjectivity of deciding Ink
Limits?
Currently I am using Onyx PosterShop 5.0 with Onyx Profiler. This new
version of Profiler uses Logo by GretagMacbeth for ICC generation, and
even though there are improvements with v5.0 over Onyx 4.5 for
generating profiles, the actual method for setting Ink Restrictions,
Threshold or Limiting, is still subjective.
In 4.5 one had to use a text editor to manually adjust the Ink Threshold
in a seperate file, and the only way to determine an appropriate level
was to continually test and reset limits, run new linearization patches,
read those and then output a file with patches that would show ink
pooling and bleeding. A time consuming process.
In 5.0 one can at least control the Ink Restriction from within the
Profiler application and they have improved the way one would test for
over inking with a new image file that can be output prior to any
linearization. But it is still subjective.
Briefly, this new file will output color patches from 2% on up to 100%
that should show bleeding, and from this one is to choose a black patch.
The instructions from the manual state >For K, find the lowest value
where saturation is obtained<. Then for the rest of the inks there are
other targets that are CMY builds of various percentages and once again
one is to >find the lowest percentage target that reaches fullest
saturation without bleeding or puddling<.
>
From this target of CMY patches a single patch now needs to be selected
which appears to be the >closest to neutral gray<. A color sampling
device can at least be used here for help in finding a patch that is
>
closest to neutral gray<. Once this patch is determined one would use
the percentage numbers that built this patch as the Ink Restriction for
the Dark Inks, setting the >lighter shades to 10% less<.
The manuel is not clear hear about light and medium inks, but with the
medium shade set to 10% less then the dark shade, what about the light
shade? Should it be set to 10% below the medium shade or both medium and
light only 10% less then the Dark Ink restriction?
What about a test file that can show problems with the transitions
between the various ink shades now that Ink Limiting is applied? Does
anyone have such a file?
Is there anyway to do this without the guess work involved?
And finally what about using the inverse of these numbers? In other
words how valid would it be to use the light and medium shades set to a
higher number then the dark ink? With v4.5 and certain medias it seemed
to help the end results, but of coarse the manual states to always set
the dark inks higher then the lighter shades when setting ink
restrictions.
Thoughts, opions, comments, a lot of questions I know, but thanks in
advance,
David Wollmann.