Re: Good demonstration of metamerism?
Re: Good demonstration of metamerism?
- Subject: Re: Good demonstration of metamerism?
- From: Ernst Dinkla <email@hidden>
- Date: Wed, 16 Jun 2010 13:12:29 +0200
Marco Ugolini schreef:
I have inspected prints made in "B&W" mode with both Epson and HP printers,
under a 100x handheld microscope. There definitely are detectable chromatic
inks in the mix, not just "neutral" ones, even when producing
neutral-looking B&W prints (i.e., no toning).
To say that chromatic inks are not being used (if that is what is implied
here) does not correspond to verifiable fact.
Marco,
I have a sheet of HP Premium ID Gloss with three 21 patches, greyscale
wedges printed on it. HP Z3100 OEM Windows driver Color mode and some
different CM settings used, QTR profile with application CM, HP's
profile for that paper + application CM and the last No CM at all. With
backlight + a 40x Olympus microscope lens + an internal microscope
measuring grid I see three kinds of grey inks used in the patches.
Approximately 40 micron round/oval dots, the light ones on top of the
darker ones in the heavier patches. Not a single CMmYRGB dot to be seen.
No MK is used for gloss so just the three; PK, Grey, Light Grey. Another
sheet with 3 wedges printed in driver B&W mode shows the same image
structure. I know from similar tests in the past that it is like that
with matte papers too that have the MK added. I know from similar tests
that no Epson Ultrachrome model has that kind of GCR/UCR in either Color
or ABW mode.
It is possible that a (grey range) profiling matching the paper white
would deliver some color dots but that has obviously not been done for
the LUTs with driver CM or the HP OEM profile in application CM. The HP
B&W driver mode uses printer CM so the same LUTs.
I'm not talking out of my neck, verifiable fact it is and I have written
similar messages more than 2 years ago after I tested the Z3100 for myself.
In contrast with that is the Wasatch SoftRip 6.2 that I can use with the
Z printer models + the profiles as delivered by Wasatch for that paper
and two other papers. It doesn't have a proper B&W driver that uses the
3 or 4 monochrome grey inks but defaults to black only by default then.
Nor is there any chance to alter the grey inks partitioning like
possible in the Quadtone RIP on Epsons. Worse is that its GCR in color
mode is way too short for such a sophisticated inkset with 4 monochrome
inks at hand. On a greyscale wedge printed on the same paper in color
mode + the Wasatch OEM profile you will see not only CMmY in the greys
from 60% downwards but even RGB ink dots. Their ink mixing algorithms
and profiling is medieval compared to what is used in HP's driver. And
it shows when I walk with two greyscale prints in my hand, one HP, the
other Wasatch created, from one lamp to the other and outdoors. Being
prone to metameric failure is one thing, it is also less consistent in
color over time and it uses way more ink. When discussed with Wasatch
they delivered some new profiles that were even worse. The rudiments of
an RGB-device mode still available in that RIP, a leftover of the time
that they couldn't make good N-Color profiles was not recommended by
them anymore. I have to agree, its hue angle/saturation choices for
replacing CMY mixes with RGB inks seems broken. So it is possible that
Z models produce color dots in greyscale images but blame it on the
third party driver then.
--
Met vriendelijke groeten, Ernst
Dinkla Gallery Canvas Wrap Actions
| Dinkla Grafische Techniek |
| www.pigment-print.com |
| ( unvollendet ) |
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