Re: UV filter or software correction or wp editing
Re: UV filter or software correction or wp editing
- Subject: Re: UV filter or software correction or wp editing
- From: Troy Buccini <email@hidden>
- Date: Tue, 25 Apr 2006 21:09:49 -0500
Hi Roberto,
I have just a few comments below form past experience.
Thanks,
Troy
On Apr 25, 2006, at 7:55 PM, Roberto Michelena wrote:
Dear Fellow Listmembers,
I'd like to hear some informed opinions about which is the best way to
go, when dealing with proofing papers with high content of
brighteners.
Case in point, using the DTP70 the proof white measures b=-8.5 ; my
target to match is Gracol v7 Beta with b=-2.
A b*-8.5 is very blue. I would suggest switching media to something
less blue if your intention is to use this to match GRACoL or any
other #1,2 press sheet. This could be a nice media as far as
printability and quality, but you will have so many issues getting
this to visually match. I did this a few years ago with a similar
media and iterated to get decent numbers and after countless edits
got a few images to match and then through some neutrals and
vignettes at it and had to start all over. This customer ended up
switching media.
So I can:
1) measure with DTP70 UV filter engaged, which gives me b=-3.2 ; the
highest dE (compared with the non-filtered measurement) is in white,
as it should (dE=5.8). However there are also differences up to 3dE in
other colors, mainly neutrals and cyans, even saturated ones.
2) try to 'fill in' the missing spectral values for ProfileMaker to
accept the data as spectral, and use the brightener correction in
software.
This only works with perceptual rendering intent.
3) using Gretag's Profile Editor, select my Gracol Profile and my
Proof Profile (made without UV filtering or correction), select abscol
mode and the output Lab->device table, and then go to 'edit workflow
white point' which will allow me to tweak down the yellow that gets
added to the background.
Which is supposed to yield more realistic (iow: accurate in terms of
human perception) results?
I'm concerned that (1) may also be cutting out some ink fluorescence,
which should not be cut out since human vision does not adapt to it
(it does consider it, as opposed to white cast to which one adapts).
I'm not sure what does (3) does, if it's just a bad hack to do so.
And (2), well, filling in missing spectral values just doesn't sound
so right, does it?
best regards,
-- Roberto Michelena
Infinitek
Lima, Peru
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