RE: How to make a linearization ?
RE: How to make a linearization ?
- Subject: RE: How to make a linearization ?
- From: Ray Maxwell <email@hidden>
- Date: Tue, 26 Aug 2003 09:42:58 -0700
>
Ray Maxwell wrote:
>
> to correct some problems you may introduce. As well as looking at
>
density,
>
> I suggest that you plot the a* and b* values for each color step wedge.
>
You
>
> just plot the a* vs. b* from you CIELab measurements. When you do this
>
you
>
> will find that some ink and paper combinations cause the Hue to change
>
and
>
> the chroma to decrease at the point that the inks reach saturation. You
>
> should set you ink limits so that you don't go past the maximum chroma
>
> point. Please note that this is another "rule of thumb". When we chose
>
ink
>
>
Graeme Gill Replied:
>
>
Of course you may be unnecessarily reducing your available gamut if
>
you do this. There would be good reason to limit the maximum
>
value of a colorant that "doubles back on itself" in its 3D trajectory
>
(since non-monotonic behaviour isn't useful, and is difficult to deal
>
with in a profiling application), but note that any colorant trajectory
>
is unlikely to be a perfectly straight line, and hence can always be made
>
to
>
appear to "loop back" when projected onto a carefully chosen 2D plane. The
>
fact
>
that a colorant trajectory looses chroma at high densities might be
>
disappointing,
>
but it is not actually a problem that needs correcting if it is still
>
extending
>
the 3D gamut.
>
>
Graeme Gill.
>
Hi Graeme,
It depends on your application. I work mostly in proofing for
offset lithography. The gamut of most of the inkjet printers I work with
are much larger than the process color gamut of the presses that I wish to
emulate. Therefore if I am concerned with accuracy and smooth behavior, I
find it easier to limit the gamut so I am operating in the more well behaved
part of the proofer gamut. However, you would have to give up some gamut to
achieve the best results when emulating the process colors of the press.
This would mean that you could not simulate as many spot colors that are
outside the process gamut of the press on this proofer. You have to decide
if you want to optimize for smoothness and accuracy in the process gamut or
maximize the number of spot color outside the process gamut.
If I were profiling a inkjet printer for use with RGB photography,
where I wanted to maximize the gamut and give up some accuracy, then I might
choose higher ink limits than for CMYK offset proofing.
Like many things in life, you have to make a choice about what you
want to optimize.
Ray
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