Re: Long, Short, Wide and Narrow Blacks
Re: Long, Short, Wide and Narrow Blacks
- Subject: Re: Long, Short, Wide and Narrow Blacks
- From: Stephen Marsh <email@hidden>
- Date: Tue, 20 Nov 2001 17:38:54 +1100
James writes:
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Hi All,
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I have seen in Henriks postings a while ago about One way to achieve a
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neutral L gray wedge is to use a long and narrow
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black UCR. Why is that? I understand what UCR is, but I am not sure
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why
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and when you would use long, short, wide and narrow blacks. Could
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someone
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please explain?
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>
James Foster
Hello James, I am sure Henrik will expand a bit on long and narrow black
UCR.
Neutral tones in a under colour removal or UCR separation will be
constructed from CMY values, which are highly device dependent - and
even on that device there may be issues hitting the target all the time.
It is my guess that a higher amount of GCR and not UCR was originally
recommended.
Grey component replacement or GCR will replace a certain amount of CMY
with K - in both neutrals and coloured areas which have a GC value to
replace with black.
UCR traditionally provides a 'skeleton' or short black plate. K is
introduced in the three quarter/shadow tones only - and only adds
density to shadow regions, neutrality is still goverened by CMY balance.
Even if you add black earlier on the grey ramp - say at 25%, then you
still have a UCR sep - but whats the point?
It is my thought that UCR is commonly used where black is not required
in coloured areas (otherwise some form of GCR would be in use). So
introducing black earlier would have little benefit for the argument of
using a UCR separation.
In theory, the separation method does not matter - all the different
mixes of device dependent colour that UCR/GCR create all equate to the
same visual or LAB value. For example, a film proof does not show the
differences between one amount of GCR or another. When the job hits the
press, thats when the balance of CMY or amount of K will show the
difference between UCR or different flavours of GCR.
UCR or GCR may be forced upon the user, as the service provider might
require a special type of separation. When the user has choice, image
content, output conditions and post conversion editing usully dictate
what type of sep is chosen, and which values are used.
I also suggest that you join this list - announce that this is a cross
post (courtesy) and repeat your general question:
http://groups.yahoo.com/group/colortheory
Hope this helps,
Stephen Marsh.