Re: Matching PANTONE colors in ColorPicker
Re: Matching PANTONE colors in ColorPicker
- Subject: Re: Matching PANTONE colors in ColorPicker
- From: Roger Breton <email@hidden>
- Date: Mon, 05 Sep 2005 10:00:01 -0400
Marco,
> ... My goal
> is to get the best possible matches possible among all the colors in the
> printer's profile working with CMYK files exclusively.
That's not off to a good start. Pantone colors should be described
independently of (press) CMYK. In InDesign, I use Lab encoding so that they
are converted directly from Lab to my Epson4000 CMYK, insuring the best
possible match.
> My goal is to find a way to provide designers with custom CMYK palettes that
> they can use in Illustrator or InDesign to achieve better PANTONE matches on a
> profiled printer in their studio than the ones they are currently getting.
See? That's not possible. You can't give designers CMYK files that are
"better" than Lab values. In InDesign, designers can use Lab but not in
Illustrator (not even IllustratorCS2!). So, in Illustrator, I tell them to
use RGB for encoding Pantone Lab values. As long as they don't have any RGB
elements in their artwork then this approach works fine.
> I start by creating a palette of PANTONE colors in ColorPicker (an arbitrary
> number of 21 in my case, just to have a group of colors to play with),
> measured directly from my PANTONE swatchbook with my EyeOne Pro
> spectrophotometer. I name each sample, then save the palette (File -> Save
> As).
Your measurements could be good or slightly off a) because of your
particular's instrument accuracy, or b) because of the particular swatch
book you bought. So, maybe you'd be better off to start off something like
Photoshop's Pantone Lab values or Color Picker's Lab values, which have been
licensed from Pantone. That way, if something goes wrong nobody can point
the finger at you.
> The next step is less clear-cut, but here is what I do: After the samples are
> measured and named in ColorPicker I open the ICC profile for US Web Coated
> SWOP v2, since this profile represents the most common CMYK standard in North
> America.
Opening bracket (moving away from the subject)
US WebCoated SWOP v2 is said to be based on TR-001 data. True. But I have a
few reservations against it. First of all, it is not colorimetrically
accurate in all respects: explain why 255r0g0b converts to 100m100y? That's
kind of serendipidity. Second of all, there isn't much difference between
the RelCol rendering intent and the perceptual rendering intent: in fact
there is barely any difference to justify spending any time in class going
over the differences between the two. Whereas profiles generated from the
same TR-001 data using other profiling packages yields vastly different
(emphasis added) perc and relcol intents. Good or bad? Some say that the
gradations of US WebCoated SWOP v2 are among the smoothest out these.
Granted. But all I'm saying is that this profile incorporates lots of tweaks
by Adobe, it's not just *a* profile based on TR-001.
Closing bracket (coming back to the subject)
> My ColorPicker preferences are the ones strongly suggested by
> GretagMacbeth in the application's help file: LogoSync CMM, Delta E 2000
> distance formula, and last but not least, an Absolute Colorimetric rendering
> intent.
Yes, this is what ought to be done. No one is going to debate that.
> I have to confess that if I use the AbsCol intent I get very lousy matches on
> my inkjet: the hues are often wrong, and the samples are overall too light. If
> I switch to RelCol, the results improve, specially the hues. And with
> Perceptual some of the colors present their best matches.
Well, you have to ask yourself why is this so? I wouldn't be surprised that
the presence of optical brightners in your inkjet paper have something to do
with those results. Unfortunately, in the present state of "affordable"
measuring technology, there are no easy receipes for taking fluorescence out
of the measurement equation. If I were you I would repeat the same
experiment with a less brightened paper.
> If I create a file with patches built from the standard Illustrator CMYK
> equivalents for my 21 PANTONE colors, put those together with patches derived
> from the values I measured in ColorPicker, and then print the file to my
> profiled printer and paper, the results are not exactly striking. The patches
> derived from my measurements do not appear much better than those from
> Illustrator's palette, at least not enough to wow anyone, specially if I try
> to use this as a promotional tool.
See? I would be willing bet you big money that the reason for this lies in
your "biased" printer profile. Not biased by you but by the measurements
which don't agree with your visual perception (and please don't anyone start
with their "Oh, just throw a UV cutoff filter in there and the problem is
solved -- there's not such magic). If you have the time, try generating a
printer profile for illuminant A (with ProfileMakerPro), recalculate your
measured Pantone Lab values for illuminant A (or remeasured them for
illuminant A instead of D50) and then reprint your pantone patches, but make
sure you observe the whole thing under a tungsten lamp, something close to
illuminant A: that way, you will be viewing the colors the same way as your
spectrophotometer "viewed" them when it measured them. In principles, you
should get better matches.
> .... here I am only interested in what can be
> done using ColorPicker to match PANTONE colors in a standardized CMYK
> environment in Illustrator or InDesign on a profiled printer, and most
> importantly WITHOUT a RIP.
Do you mean to say that you are profiling in RGB?
Regards,
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden