Re: linearization - luminance, chroma or density?
Re: linearization - luminance, chroma or density?
- Subject: Re: linearization - luminance, chroma or density?
- From: Marco Ugolini <email@hidden>
- Date: Tue, 23 Jan 2007 22:30:37 -0800
In a message dated 1/23/07 7:31 AM, Clark Omholt wrote:
> This is an area where we've done a fair amount of investigation. The
> RIPs we've worked with most are EFI Colorproof XF/Best (Lab), Onyx
> (density), Colorburst (Lab), ImagePrint (no linearization currently).
> The ones that use Lab I believe use chroma for linearizing colorants and
> L* for linearizing K.
>
> Our experience has shown linearization to be pretty mechanistic,
> resulting in good results in combination with an ICC profile using
> either density or Lab. The area to pay the most attention is in
> per-channel ink limits. There's a number of reasons for per-channel ink
> limiting.
Hi Clark.
You mention ColorBurst: I assume you mean XProof.
I have felt disappointed with the Mac version of this RIP lately, specially
since ColorBurst decided to take away from the user the direct controls that
it used to offer via the Printer Settings command over parameters such as
print resolution, paper type, dot size, and ink type.
Now the user of the Mac version is forced to start from one of the standard
environments, which is trusted to include the correct choices of resolution,
dot size, etc, hopefully the correct ones for the paper being used, then
relinearize and profile starting from that (with the added burden of having
to use a UV-cut spectro -- but that's another subject yet...).
I just went through a tough time linearizing and profiling Epson's Single
Weight Matte Paper on a client's 4800. Two problems proved to be big
head-scratchers:
1) After linearizing and profiling, the print had a distinct yellow tone in
the highlight areas where there was any value at all above pure white. (This
was not the kind of even yellowish tone that may appear when using an AbsCol
intent, but instead localized areas of yellowish tone that followed the
shapes and locations of the highlights in the image that carried something
close to a minimum value this side of pure white.) I was able to fix that
through a hack that I made up on my own (I became sure that my non-UV
linearization was creating the problem, and I was proven right: when I used
the canned linearization and profiled on top of that, the output finally
appeared normal in the highlights).
2) The shadow areas were heavy and plugged up, far more than would be
reasonable to expect in a matte paper. There was considerably more ink in
those areas than was to be expected in the circumstances. (Incidentally,
even using the OEM environment, the shadows appear similarly heavy.) I used
the per-channel ink limits that came with the environment, but I wonder what
procedure I could use to determine them with more precision. I am at a loss
for the time being, and I also don't have the time and the consumables to
try different possible solutions. Do you have a tested-and-true procedure to
determine the per-channel ink limits in ColorBurst XProof? And on top of
that there is another ink limit setting to grapple with (320% in the OEM
environment). The mystery does thicken considerably...
Any advice would be welcome.
Be well.
Marco Ugolini
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