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: Todd Shirley <email@hidden>
- Date: Tue, 29 May 2007 16:25:02 -0400
On May 29, 2007, at 3:16 PM, Terry Wyse wrote:
Just curious Todd, did you find that when measuring papers with UV
EXcluded that all of your spectros measured paper white more-or-
less the same/more consistently (< 1dE)?
Of my 3 devices (Spectrolino, iSis & i1pro), only the iSis has the
ability to cut UV, so I can't test this. The i1pro can't be changed,
and for some reason I don't have a UV filter for my Spectrolino .
In the world in which I live (inkjet contract proofing systems)
where you might generate your own source data but where we are
increasingly relying on "standard" characterization data such as
GRACoL2006_Coated1 or perhpas FOGRA data sets, these are, by
definition, created/measured with UV-included. So if you were to
use one of these standard data sets/profiles but you created your
destination profile with a UV-cut spectro, your visual match would
not be correct. There are ways around this but unless you're using
something like a GMG RIP, which allows direct editing of
measurement data ("target values"), it can get pretty ugly trying
to edit profiles to compensate for this difference. The accepted
standard for pressroom measurements and characterization data is to
use UV-included measurements so that's basically what I've stuck to
with most of my spectros.
You say the standard data is "by definition" with UV-included. This
is only relevant if the paper the characterization data was taken
from has optical brighteners, right? As far as my (limited)
understanding goes, UV only effects OB readings, and thus is more-or-
less limited to the highlights and paper white, and then only if the
paper actually HAS OBs. If this is indeed the case, then it would be
extremely important to know what paper the characterization sets are
from and how much optical brighteners are involved. This brings me
back to my original point, which is there is no official language to
specify how much, if any, optical brightener is in a paper. I guess
since these data sets are averaged and "smoothed", then the optical
brightener content would be some sort of average as well, but surely
this isn't the same amount of OBs that are found in most inkjet
proofing stocks.. or is it?
If it were me, I'd stick with a spectro that offers BOTH options
(DTP70, iSis, Spectrolino) or simply purchase two Eye-Ones so
you're covered either way.
The thing about the iSis, as I understand it, is that in order to
take UV-included measurements it actually takes 2 readings of each
patch, using different illuminants, and then does some sort of
averaging to come up with the Lab value. This has the effect of
making the whole device run at half the speed that it runs in UVcut
mode, where it is only making one measurement of each patch. It also
means, in my limited testing, that the UV-included measurements are
somewhat different than the UV-included measurements off the i1pro,
which is only taking one measurement with no filter, but with a
different illuminant.
I believe the DTP70 (which I don't have) simply has a mechanical
switch for using the UV filter, which means it runs at the same speed
in both modes and just seems to make more sense than the iSis method.
Of course they don't make the DTP70 anymore! The Spectrolino also
seems more logical, in that you just mechanically change filters.
Also no longer in production! And of course your solution of buying 2
Eye-Ones does has the nasty side-effect of doubling the price. So you
just can't win!
-Todd Shirley
Urban Studio
New York
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