Re: Creating ICCs with pigmented inks
Re: Creating ICCs with pigmented inks
- Subject: Re: Creating ICCs with pigmented inks
- From: Chris Murphy <email@hidden>
- Date: Tue, 2 Jul 2002 13:28:50 -0600
Graeme Gill <email@hidden> writes:
>
Our test runs on the Epson Glossy film with the Dye ink
>
gave the following results:
results snipped
>
ie. appallingly bad for proofing purposes.
OK, but first of all I would personally never consider using glossy film
for proofing purposes. Second, is that the only paper you have results
for? It's not an adequate sampling to place a blanket label on the
stability of dye based inks. It wouldn't surprise me at all if pigment
inks are more stable on plastic than dye inks.
>
> The problem with the pigment based inks used in the Epson 2000, 7500,
>
> 9500 and 10000 w/ pigment ink option, is that they are extremely
>
> susceptible to metamerism.
>
>
What makes you say that ?
Uhhh - experience actually seeing lots of Epson 2000, 7500, 9500, and
10000 (with pigment inks) prints under various lighting conditions, and
seeing absolutely absurd color shifts.
>
The spectral characteristics of the pigment
>
inks is not that dissimilar to other media, and in any case, none of
>
these 3 or 4 color systems are capable of anything other than
>
a metameric match.
I totally disagree. I've used the HP 5000 with pigment inks, and a couple
of other pigment ink sets and the spectral characterstics among them is
not the same, and the behavior of neutrals is also very different. Of all
the pigment ink sets I've worked with, albeit not that many, the inks
used in the listed printers has the greatest illumination dependency I've
seen with any method of output.
>
The implication of course is that you will
>
only get a perfect match under the lighting conditions (and with
>
the observer) it has been set up for. The research I've read on spectral
>
matching indicates that you need something like 6-8 carefully selected
>
inks to hope to do well at this, and as far as I'm aware, there
>
are no commercial proofing systems that claim spectral matching.
The problem isn't spectral matching because that's not possible anyway,
without using the exact same pigment (and probably carrier as well) used
on press.
The problem is that this inkset strongly discriminates between the D50
and F7 or F8 illuminants. D50 LAB is what is used for building ICC
profiles, yet that is not what is commonly used for proofing - but rather
the F7 or F8 illuminant. While they have a correlated color temperature
of 5000K, they do not reproduce the spectral power distribution of D50. A
lot of times this is not going to cause that much of a discrepency, but
with certain inksets it causes a huge discrepency and the Epson pigmented
inks used in the listed printer models use one of those inksets.
>
It is easy to get very stable neutrals using pigment ink simply
>
by maximizing the black usage.
Graeme, the problem starts in the highlights. You can't start black that
early or you end up with grainy pictures. The amount of black generation
needed to virtually eliminate the problem makes it easy to see black dots
in the image. I speculate that's one of the reasons we have a light black
ink with the new 2200 - so that more black generation can be used in
neutrals to mitigate metamerism while not seeing big black dots in the
prints.
>
We certainly haven't seen any worse
>
behaviour in this regard on the 10000 pigment than any other
>
inkjet device.
Well you're the first I've heard this from. We aren't talking subtle
shifts here. Naturally even with dye based prints you have metamerism but
it's no where near as bad as pigmented inks in the listed printers. I'm
talking about green cast people in daylight (alien green) to sunburned
in incandescent. Should people be looking at proofs in these lighting
conditions? No they shouldn't, but they do it all the time because
they're used to it. These inks are highly illuminant dependent and are
simply not usable where the light source can't be rigorously controlled,
and given the near total lack of control of standard lighting in the U.S.
it would be (and has been) a problem using these printers for proofing
purposes. Heck it's even been an even bigger problem for photographers
where they have no idea where their printed artwork will end up - and
that's a case where you would want 70+ years of stability.
>
Stable neutrals doesn't mean that it matches
>
the target media though, since the target media is also
>
subject to metamerism, and its neutrals may change under
>
the different lighting. Something closer to a spectral
>
match is probably a proof that has a similar CMYK composition
>
to the target (which is what we have done).
>
>
> Uhh, because for proofing, it works, that's why. If you want a long
>
> lasting print, go pigment.
>
>
Most of our customers are looking for a proof that will be useful
>
for at least a couple of weeks, if not as long as a year. Pigment
>
works for proofing, whereas our experience with dye indicates that
>
it isn't stable for even a week.
Yeah when printing on plastic. Your sample size is nowhere near big
enough to make a blanket statement that pigment inks in Epson 2000, 7500,
9500 and 10000 yields universally better results for proofing purposes
than dye based inks. I don't know a single credible vendor in the U.S.
pushing these particular pigment based printers anymore because of the
problems people have experienced with it.
Now the new Ultrachrome inks used in the 2200, 7600, 9600 are awesome in
comparison.
>
But having them be stable for a couple of weeks is.
I haven't had this problem, and so far you've only mentioned tests with
glossy film.
Chris Murphy
Color Remedies (tm)
Boulder, CO
303-415-9932
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