Re: UV filtered vs. non UV filtered spectros
Re: UV filtered vs. non UV filtered spectros
- Subject: Re: UV filtered vs. non UV filtered spectros
- From: Roger Breton <email@hidden>
- Date: Tue, 29 May 2007 21:14:23 -0400
Terry, Graeme and the others have done an excellent job of outlining some of
the pitfalls typically associated with UV-filtering. Let me add a few of my
own.
It's true that most printing papers now have some level of OB added to them.
So, OB-filled papers are a fact of life.
Now, what's important, to me at least, is to keep in perspective the exact
application where the measurements will be used.
As Terry mentioned, when trying to match measurements or existing ICC
profiles corresponding to "standardized" or "idealized" or "synthetic" or
otherwise smoothed or massaged data, nine times out of ten, one can be sure
that the data represent un-filtered measurements. This holds true, I find,
for TR-001:1995, all the ISO-12647-x series, SWOP 2007 and GRACoL 2007, and
all the Fogra stuff.
I can think of some applications where using a UV filter on the instrument
is a no-brainer, like Cougar Opaque who fluoresces like '70s disco's black
lights.
But it is less obvious for papers that are under CIE b* < -4 IMO.
Especially when doing custom press profiling work.
I recently completed a custom press run where I measured as series of
samples with and without a UV filter on the instrument (i1pro), and the
results surprised me. As far as converting from, say, RGB to CMYK, it didn't
not matter which sets of measurements were used to build the press profile
as both resulted in the exact same gray balance curves and gamut mapping
(!). Surprising indeed. (when you think about it, it makes sense) The only
place where the two sets of data made a noticeable difference is in the
AbsoluteColorimetric rendering: with UV-excluded measurements, the media
white is represented very neutrally in the profile (a* and b* close to zero)
but so with the UV-included measurements. There, the substrate is rghtfully
seen as bluish and will be carried forward as such to the proofer profile.
Whether this agree with visual observations of an actual press sheet on the
proof is another story. But we'll leave it at that.
Color management is so simple, in principles, but in practice, even with the
right tools, call me nuts, but it remains a black art.
Anyway, getting back to the main point of the original poster, I'd say, for
press work, unless the substrate is b* > 5, 6, 7, I'd leave the heavy UV-cut
artillery in the drawers.
Roger Breton | Laval, Canada | email@hidden
certified color management enthousiast
http://pages.infinit.net/graxx
> I am trying to weigh the pros and cons between getting a UV filtered
> spectro (probably an EyeOne) and a non UV filtered spectro.
>
> I will be profiling a variety of papers, some with optical brighteners,
> some without, printed mostly on digital presses. The lighting under
> which the final prints will be viewed will vary: incandescent,
> fluorescent, natural light.
>
> I'm wondering if the safest way to go is to go UV filtered. I'm
> considering going with ProfileMaker, which apparently has software
> correction for OBs, but I'm not sure if it can be relied on.
>
> Any recommendations or thoughts to clear up my confusion on the way to
> go with this would be most appreciated.
>
> Thanks,
>
> Matt Larmour
>
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