AW: ink restrictions
AW: ink restrictions
- Subject: AW: ink restrictions
- From: Peter Henry <email@hidden>
- Date: Mon, 18 Dec 2000 11:38:40 +0100
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Message: 14
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Date: Thu, 14 Dec 2000 16:19:44 -0700
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From: David Wollmann <email@hidden>
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Reply-To: email@hidden
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Organization: Luna Vista Imaging
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To: ColorSync <email@hidden>
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Subject: ink resrtictions
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Also the overall gamut of a particular
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ink and paper combination is greatly affected by Ink Limits.
[Peter Henry] Yes but not as sigificant as it seems to be. you'll
have at the colorspans more the problem of a coarse output with peppering
effects
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Vinyls and canvas can be problematic when using pigmented inks. These
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materials seem to need very high levels of ink limiting in order to
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avoid bleeding, and as a result the gamut suffers. So, I want to find a
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way of finding that elusive edge between over inking and reducing the
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Ink Threshold more then necessary.
[Peter Henry] I'm doing it in that way that I set the m3 and c3
threshold as high as possible so that the 200% red green and blue on the
darkinkrestrictions.tif are just becoming dry in the normal print process.
this due to have the maxium possible hues. the cmy and cmyk gradident on
that tif will be controlled by the ink limit in profiler later.
you could use a desitometer to measure the max dens but I would't do
this cause to what will you refer to? some times I use the max denses of
euroscale (fogra) but just as an Idea where I am...
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Is there any method that can remove the subjectivity of deciding Ink
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Limits?
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[Peter Henry] well color is allways subjective ;-) there is nothing
like a clear manual for this. even onyx has no absolute clear way for that
procedure. and I guess there is definitly none
[Peter Henry] I personally never use the "L's" descibed below. I
prefer the use of the profile generator and use later a hand optimizing of
the profiles in the editor in order to get a good gray. but to be honest you
can not do this in a sufficient way with the logo editor. I prefer the
colorblind edit and optimise the gray under the output gray ballance
funktion...
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The manuel is not clear hear about light and medium inks, but with the
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medium shade set to 10% less then the dark shade, what about the light
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shade? Should it be set to 10% below the medium shade or both medium and
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light only 10% less then the Dark Ink restriction?
[Peter Henry] yes this is the idea. what I do is I use a raster
microscope and adjust the thresholds in that way that the dark pixels are
starting in the brighter inks more late as early in order to avoid
peppering. this can be 10% less but sometimes I keep it at 100%. the bright
ink is decresing in a 450 angle from 100% on into direction the dark
channel. that means it reaches at 75% of the whole colorchannel the 0% line
In the case colorspan this means the light ink goes from 0%-33% and
decreases then till 66% the medium starts at 33% til 66% and decreases then
till 100% the dark ink start at 66% til 100%
that the reason why you feel getting better results with having as
much bright ink as possible.
this is exactly the same experiance what I have.
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What about a test file that can show problems with the transitions
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between the various ink shades now that Ink Limiting is applied? Does
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anyone have such a file?
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[Peter Henry] my impression is with postershop that as soon as you
switch profiles on especially with the colorspan you'll see steps in your
gradients. if you switch profiles off the gradients will be perfect.
I do have this kind of experiance also with other rips. might be a
good question to the usergroup whether this is an often made experiance
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And finally what about using the inverse of these numbers? In other
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words how valid would it be to use the light and medium shades set to a
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higher number then the dark ink?
[Peter Henry] why not. from onyx's side it is not logical to do
this and it is not. in the case of a colorspan it makes sense cause you are
getting smoother transitions. this is exactly what I have seen here. as you
know that the medium ink in decreasing until 100% constantly you can use it
even until the deep ares of the colorchannels. so you use the dark inks only
for the very deep areas 80%-100%
This is not an easy area and the systems are far away from beeing
plug and play :-)
hope that helps a bit
Peter R. Henry
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Gretag Professional Imaging Division GmbH
European Management Technical Sales Support
72336 Balingen