Re: Creating ICCs with pigmented inks
Re: Creating ICCs with pigmented inks
- Subject: Re: Creating ICCs with pigmented inks
- From: Graeme Gill <email@hidden>
- Date: Wed, 03 Jul 2002 12:03:40 +1000
Chris Murphy wrote:
>
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
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stability of dye based inks. It wouldn't surprise me at all if pigment
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inks are more stable on plastic than dye inks.
Fair enough, we're going to do some test runs on the
proofing media to see if its any better, but the dye
made a very, very bad first impression !
>
I totally disagree. I've used the HP 5000 with pigment inks, and a couple
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of other pigment ink sets and the spectral characterstics among them is
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not the same, and the behavior of neutrals is also very different. Of all
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the pigment ink sets I've worked with, albeit not that many, the inks
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used in the listed printers has the greatest illumination dependency I've
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seen with any method of output.
We're not talking the same language. There is no such thing as
an ink which is "illumination dependent", unless it is photosensitive.
They just have different spectral reflectance characteristics. If
the shape is similar enough to the target ink, then they will match
under a wide range of illuminants (they are a good spectral match),
and if they are rather different (extreme, think CRT spectra vs. print),
then they will be a good match under a more restricted range
of illuminants. Unless you are very lucky, or choose your
inks to match just one target, 4 inks is not enough to create a general
purpose spectral matching based color reproduction system.
There is one degree of freedom to play with (the amount of black),
so you can do a very crude first order attempt at spectral
matching, but in general you can only expect to get a perfect
metameric match, and this can only be achieved under a known
lighting condition with an assumed observer.
>
The problem isn't spectral matching because that's not possible anyway,
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without using the exact same pigment (and probably carrier as well) used
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on press.
But it is possible if you compose the spectrum out of enough
selected inks. Its just complicated and slow, and is only
at the research phase at the moment. Such systems are being
researched for fine art reproduction etc.
>
The problem is that this inkset strongly discriminates between the D50
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and F7 or F8 illuminants. D50 LAB is what is used for building ICC
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profiles, yet that is not what is commonly used for proofing - but rather
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the F7 or F8 illuminant. While they have a correlated color temperature
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of 5000K, they do not reproduce the spectral power distribution of D50. A
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lot of times this is not going to cause that much of a discrepency, but
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with certain inksets it causes a huge discrepency and the Epson pigmented
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inks used in the listed printer models use one of those inksets.
Maybe on some profiling systems, but the better ones let
you choose the illuminant you will actually be using :-)
>
>It is easy to get very stable neutrals using pigment ink simply
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>by maximizing the black usage.
>
>
Graeme, the problem starts in the highlights. You can't start black that
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early or you end up with grainy pictures.
Only if your dot size is large. Luckily the 10000 has a dot size
small enough to get away with this.
>
The amount of black generation
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needed to virtually eliminate the problem makes it easy to see black dots
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in the image. I speculate that's one of the reasons we have a light black
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ink with the new 2200 - so that more black generation can be used in
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neutrals to mitigate metamerism while not seeing big black dots in the
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prints.
It's certainly a welcome move, although I think that with the
upcoming generation of printers the presence of "light" inks
isn't actually needed anymore, and it would be better to
do away with them. Give me more dot sizes, not more inks!
Marketing pressure will ensure they are around for years to
come though :-(
>
Well you're the first I've heard this from. We aren't talking subtle
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shifts here. Naturally even with dye based prints you have metamerism but
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it's no where near as bad as pigmented inks in the listed printers. I'm
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talking about green cast people in daylight (alien green) to sunburned
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in incandescent. Should people be looking at proofs in these lighting
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conditions? No they shouldn't, but they do it all the time because
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they're used to it. These inks are highly illuminant dependent and are
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simply not usable where the light source can't be rigorously controlled,
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and given the near total lack of control of standard lighting in the U.S.
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it would be (and has been) a problem using these printers for proofing
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purposes. Heck it's even been an even bigger problem for photographers
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where they have no idea where their printed artwork will end up - and
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that's a case where you would want 70+ years of stability.
Again, it depends on the color setup and the RIP. Obviously
there are some who have done it badly. Pity the ink has been
blamed for it. It may well be that the pigment give a worse
spectral match to typical printing inks than the dye, but
the question is whether this leads to noticeably poorer results
under non-standard illumination conditions. Our experience
is that done properly, the pigment seems no worse than
dye and other inkjet systems in this regard. The one
think I don't like so much about it is the amount of
bronzing it has. The Ultrachrome is even worse in this
regard.
>
Yeah when printing on plastic. Your sample size is nowhere near big
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enough to make a blanket statement that pigment inks in Epson 2000, 7500,
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9500 and 10000 yields universally better results for proofing purposes
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than dye based inks. I don't know a single credible vendor in the U.S.
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pushing these particular pigment based printers anymore because of the
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problems people have experienced with it.
But blanket statements are being made canning pigment,
when I have the evidence in front of me that it is probably
the best overall choice. The fact that some people don't seem to
have the tools or knowledge to make profiles for it, isn't
a reason to claim that it's inherently no good.
>
Now the new Ultrachrome inks used in the 2200, 7600, 9600 are awesome in
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comparison.
As I understand it, Ultrachrome is a development of the pigment ink !
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>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
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glossy film.
So its pot luck as to whether it is stable or not ?
Graeme Gill.
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