Re: colorsync-users digest, Vol 3 #449 - 16 msgs
Re: colorsync-users digest, Vol 3 #449 - 16 msgs
- Subject: Re: colorsync-users digest, Vol 3 #449 - 16 msgs
- From: Graeme Gill <email@hidden>
- Date: Wed, 16 Oct 2002 12:05:04 +1000
Marc Levine wrote:
>
While we're making clarifications, I figured I'd jump in with my obligatory
>
colorsync posting. Regarding the whole UCR GCR issue, I would think about it
>
like this... The problem with digital proofing is that the ink and media
>
sets you are using to make proofs are miles away from those which you are
>
using to produce your press sheet. Even if you define the same laws for
>
UCR/GCR settings, your proofing profile will STILL be dramatically different
>
that the press profile due to the "intelligence" that a good
>
profile-building application will use when computing separations. In other
>
words, don't be biased by the construction of your source profile. You ARE
>
going to Lab, from which you should be intent on building the most accurate,
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dynamic data that you can - that's what a good output profile will do for
>
you.
The passing through of black level is only some advantage
on particular proofing devices. On many, it isn't worth
much, because you can't actually tell how much black
the proofing device has used (ie. color copiers, and inkjets
with high resolution or light black), and you can therefore
simply maximise it, to improve the robustness of the result.
For inkjets that have a lower resolution (ie. you can see
the dots with the naked eye), and/or don't have a light
black to use, it can be an advantage to bias the proofing
output black level to match the input. This causes original
neutral areas (like black text) to be reproduced using
mainly black, maintaining a good neutral independent of
the lighting independence at the cost of some visible dots,
while composite originals such a photos are reproduced with less
black, giving a smoother less dotty result, at some cost to the
neutrality under uncontrolled lighting conditions.
What happens is that you build a profile by linking together
the source and destination, and augment the intermediate Lab
values with a "black level" number (meaning that you
are passing 4 dimensional information between the two
profiles in a device independent way), and lookup a proofing
device value that has the required Lab value, and has a black
level close to the value of the original. There is actually
a continuum between completely regenerating the black,
and passing the original intent through as faithfully as possible.
Another advantage of using device links, is that you can take
more time about creating the original profiles and linking them,
than a system that needs to link them on the fly, in real time.
>
Anywhoo, don't get hung too up on your proofer profile settings - a good
>
profile building package should make a good profile. Hope this helps.
Proofing RIPs can offer many other features specific to the task,
that aren't generally on offer with a generally purpose RIP and
profiling software, such as handling various image setter format
files, plane separated files, reproduction of original screening/descreening,
emulation of spot color plates, automatic addition of verification
wedges etc.
Graeme Gill.
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