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: Graeme Gill <email@hidden>
- Date: Wed, 30 May 2007 11:26:55 +1000
Todd Shirley wrote:
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
The OB's affect a wide range of colors. Even something like a 90%K
reading is noticeably affected by OB's (ie. delta E 2).
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.
There are various attempts to quantify such things. In the paper trade
I believe they compare paper brightness without, and with 400nm and
420nm UV cut filters as a way of doing so. Also ANSI CGATS.5-1993 annex B
(and possibly later standards) has some recommended approaches to
assessing fluorescence in measurement.
> 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?
One approach to dealing with OB's in proofing is to try and match
the level of OB's between the target and proofing media.
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!
There is another approach, which is to compute the UV excluded using
FWA compensated readings for a D50 spectrum that's been shorn of it's UV.
The results appear to be quite close to what a UV excluded instrument would
read, which is what you'd hope for if the FWA is working correctly.
(This was using my ArgyllCMS).
Graeme Gill.
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