Re: Out Of Press Gamut (rewrite)
Re: Out Of Press Gamut (rewrite)
- Subject: Re: Out Of Press Gamut (rewrite)
- From: Roger Breton <email@hidden>
- Date: Fri, 23 Dec 2005 22:35:50 -0500
Bill,
> After reading some of the responses to my post and then re reading my
> original post I realized that what I thought I had written as clear
> and concise, was not.
Words are everything.
> Since I REALLY value the feedback I receive from this digest and
> would like more feedback on these issues I will explain my challenges
> (2) with more (hopefully) clarity.
OK.
> Definitions:
> Press Images Sheet - this is a sheet of images we printed on the
> press after making the press profile.
Do you "sheet" inline your flexo web? So "press images sheet" means a series
of test images that were color managed through your custom press profile.
OK. I understand better.
> Proof Images Sheet - same images file that was used to print press
> images sheet. This was printed from the 4000 and then adjusted to
> "match" the press images sheet.
I get it. These are the proofs. They are supposed to match or simulate the
Press Images Sheet. Did you use AbsCol? I guess that was one of the earlier
comments. I'll suppose you did.
> Background review:
> Flexo printer
Paper substrate as opposed to poly, I gather now.
> DTP41 used to read ECI2002 target from press and proofer
UV or no UV "DTP41"? ECI2002 targets formatted for the DTP41 means your
flexo press must have a huge repeat like 24" and more in order to fit the
ECI2002 targets formatted for the DTP41. Otherwise, you must have had to
spread your targets on more than one press form.
> EyeOne used to make spot measurements on images (press and proofer)
> sheets
We'll assume there is a good correlation between the DTP41 and the
EyeOnePro, otherwise you would be comparing apples with oranges.
> Profilermaker 5.02 used to make profiles (press and proofer)
Nothing wrong with ProfileMakerPro v5.02.
> Epson 4000 with Ultrachrome inks
Nothing wrong with that printer and those inks.
> Epson Proofing Paper Semimatte
That paper tends to appear on the yellow side as opposed to bluish. It has
an L* of around 93 to 94. Handles very nicely.
> Press paper is semigloss
Some coated glossy substrate. OK. What is the Lab value of your press paper,
by curiosity?
> Best v5.0 SP2
That RIP should do the work and there are many ways to set it up. We'll
assume it is set up properly to simulate the press dynamic range. But ginve
your flexo inks, you may run into press colors that are out of gamut of the
Epson 4000 just by the sheer saturation of some the flexo inks that are used
in some industry, which yours may very well fall into. Depends on how "pure"
you run your ink. Any dilution with solvent? What kind of viscosity, 27 to
30 seconds?
> Both ECI2002 target and Press Images Sheet went through same workflow
OK so we now your color workflow is repeatable.
> Challenges:
>
> 1 - Proof images sheet does not match press images sheet.
There are many reasons that could account for this. And it is not uncommon
at all.
> I received
> some good suggestions for this challenge including; upping resolution
> of proofer to 1440 x 720 (have already done that);
I don't see how that would help, logically? Most places I run into operate
their Epson UC printers at 720 in the interest of speeding up the proofing.
> trying different
> papers (have tried one and have another on the way);
That one is a big variable. But as long as it is no darker than the press
paper you should be able to proof AbsCol on it.
> and white point
> adjustment (will try that upon return to the office after Christmas).
I am not too fond of white point adjustment. But, if it helps.
> One other suggested covered TIL. I played around with that by adding
> my own value in the TIL result box in the second step of Best RIP
> linearization sequence.
On the press or proofer side? You want to restrict as little as possible on
the proofer side. On the press side, it's a matter of judgement but anything
too high, like 330 and up, is probably not going to give you any extra.
> I do not have Best Premium so could only add
> one number.
If it's anything like the current Premium, I don't see this as improving
your situation. My experience even suggests otherwise. But, as it's often
said here, your mileage can vary.
> I ran a cmyk ramp file through the uncalibrated queue and
> discovered that the L value was lowest when all cmyk values were 88%.
> I entered 352 in the TIL result box in an attempt to get more color
> on the proof sheet (larger gamut?). But it did not seem to make much
> difference when I built the subsequent proofer profile.
You mean it did not make much difference given the set of images you used?
Did you actually reprint your serie of test images at the 352 TIL? It will
only register if you start from RGB images that have dark enough tones to
benefit from the extra TIL.
> I also
> discovered that even though Best reports a 207 in the TIL result box
> when I printed out the report and added the cmyk values listed on it,
> the sum is usually in the 320 range.
That's expected. It's one set of numbers mapped onto another set of numbers.
But you're going about it the right way, IMO.
> What is the 207 number all
> about?
It's 207 TIL in the printer system, nothing to do with the press TIL numbers
as I was saying above.
> By the way when I printed the ramp I was able to print 400%
> ink without puddling.
You mean on the proofer or the press?
> In an attempt to make the proof images sheet match the press images
> sheet I have iterated the profile, added a cyan curve and made 4
> edits to the B to A table of the proofer profile. I have had limited
> success as the colors are closer between the proof images sheet and
> the press images sheet but still not close enough for me.
OK. Editing the profile is sometimes the only route to improve the
situation. But in your case, there must be some other factor at play.
> 2 - Press images to press gamut problem. This challenge DOES NOT
> include the Epson, only the press. One of the colors I am having a
> big problem with when comparing press images sheet to proofer images
> sheet is a light red (6% M, 17% Y).
What is the Lab value of that color in your press profile?
> I measured this color,
Measured it where? On the press sheet?
> plotted it
> in ColorThink and it is in the proofer gamut BUT it is floating above
> the press gamut.
Can you send a screen grab?
> If the parameters / tolerances to run the ECI2002
> target used to make the press profile are the same as the ones used
> to run the press images sheet how can this be?
There is something that is not clear to me in your explanation about that
light red color, Bill. If it is 6M and 17Y, then it must have some mapping
(correspondance) in the press profile. So that device color must exist
somewhere WITHIN the gamut of your press profile *by definition*. I suspect
you are confusing it with some other device gamut, could it be?
> Parameters /
> tolerances between two runs were; cmyk inks within .5 delta E, same
> paper, correct densities, correct dot gain.
Wow! Excellent process controls.
> While I could not find
> the exact values (6% m, 17% y) in the ECI2002 target I did find
> colors below these values so I would guess that I am not printing a
> color on the press images sheet that the profile did not have a
> chance to create by reading the press printed ECI2002 target.
Right. So it sounds like the results of some faulty profile manipulation.
Could it be?
> So with
> my limited education I would guess that any cmyk color mix I
> subsequently print on the press will fall within the press gamut,
Wait! You will have to specify *where* that subsequent cmyk color mix comes
from.
> -Bill-
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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