Re: To UV or not
Re: To UV or not
- Subject: Re: To UV or not
- From: Roger Breton <email@hidden>
- Date: Wed, 20 Sep 2006 22:42:48 -0400
> Either way though, wouldn't it be logical
> that the best results would come from the workflow where the press
> target data, and proofer data are both measured with the same
> filtration?
Yes, I entirely agree with you.
And that's the hypothesis I was toying with, to have the press sheets
measured with the UV filter ON. But that's 56 sheets to measure, you know. I
was trying to avoid that pain.
On the other hand, the #3 press paper I used for this test did not, IMO,
exhibited significant FWA, simply looking at its spectral reflectance curve.
So, being mildly blue, I reasoned that re-measuring the press sheets through
the UV filter would not make such a big difference.
> That has been my experience (for the most part anyway).
As a rule, I always try to measure press and proof using the same
instrument. But, you know, I have created a number of press profiles out of
Spectroscan measurements. When I have to create the proofer profile at some
client site to simulate those press profiles, it is more convenient to carry
a DTP70 around than a Spectroscan table. Yes, I have to live with the
inherent calibration differences between GMB and X-Rite instruments :(
Keep in mind too that there are lots of datasets around, the FOGRAs for
example, that have been measured with a Spectroscan: does everyone use
Spectroscan to create the corresponding proofer profiles? Hmmh. So everyone
lives with the colorimetric mismatches.
> Have you tried a press profile with UV excitation excluded?
I will give it a try on a smaller number of press sheets.
> I would expect
> the proofer profile with UV excitation excluded to be closer in that
> case, no?
If the press sheet shows little fluorescence, to measure with or without a
UV filter will not make a difference, you know. That's the traditional
X-Rite stance anyway.
> Does your proofing stock contain FWAs?
Ah yes. Not lot's like b* of -7 but enough to cause the proof to look overly
yellow compared to the press sheet. The current proof paper I use has a b*
value of -4.5, depending on which instrument I use to measure it.
Today, I went back to MidState Graphics's ProofLine PressWhite160. The
results : much closer to the press sheet and with *NO* UV filtration. This
paper has a b* of -2 and does not exhibit any hump in the 420-440nm range. I
think I'll soon switch paper. But I need to experiment first with GMG
SemiMatte 250 and Oris PearlProof SuperWhite which contains absolutely no
traces of FWA none whatsoever. Then I'll take my pick.
Regards,
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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