Re: Printing problem...
Re: Printing problem...
- Subject: Re: Printing problem...
- From: Martin Weberg <email@hidden>
- Date: Mon, 2 Nov 2009 11:57:45 +0100
Hi,
2009/11/2 t labarbera <email@hidden>:
> Onscreen they look great;
I guess this is a high-end monitor set-up calibrated and characterized
according to standards?
> the printer's proofs (calibrated inkjet) look great.
If "calibrated" is the only information you get from a
printer/prepress shop about it's proofing system, then you really
don't know anything. Calibration, characterization and simulation is
all proofing elementary. You need to know what they are simulating
according to what standards/colour space. Are they printing according
to those standards too?
> Much of the printed job is problematic. Many of the new images have a magenta or yellow cast.
Not good having different casts if it is the same type of images.
Indicating a non-stable process. Or maybe the images are on different
sheets and they have a problem matching sheet-to-sheet, yet non-stable
process.
Another possibility with different casts, depending on the imposition,
is that there are images on the same sheet lining up in the printing
direction requiring different amount of inks making it impossible to
match both images.
> The client and I met with the printing company; they claim the color shifts we see are normal, within press tolerance.
It's hard to tell without looking at those prints/proofs. Are they
using some process control system? Is it possible to measure colour
bars on the sheets? What tolerances do they have, in numbers? If the
prints are within the printers specs, maybe their tolerances are too
liberal.
> Now I know why the older images are gray scale! However, we like the richer look of the new images. What can I do to minimize the press issues? One thought I had was to use a much more aggressive GCR for the pages with this kind of image.
That's exactly what you can do.
> It shows they image to have very little K (1-10%), even when the CMY values are something like 45 48 52.
A "normal" separation would have K around 30-40% and now you could add
even more.
> For this printing, I allowed Distillier to convert the RGB images to CMYK."
Well, that should be no problem.
> When I asked him about any sort of press profile, he reported the following--he's based in the US:
> "The printer had no special profile. They asked for US Sheetfed Uncoated v2. The proof is OK. Perhaps 20% of the run is OK, but the rest varies. I think the issue is that with very neutral images, small variations in ink (esp M) become very visible."
Maybe their process are not set-up according to US Sheetfed Uncoated
v2 and the printers struggled to get close to the proof. But it sounds
like they are having a process stability issue.
Re-separation of images, using more GCR, may not necessarily solve
your friends issues. It is possible they have a problem and are
covering it up talking about tolerances (we have nothing to loose,
let's try fooling our costumer...).
Sadly this is a common situation. Lots of things to look into here and
more information is needed. This is exactly why printers need process
and quality management systems. To end the guess-work.
Martin Weberg
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