Re: Yellow too high on GRACoL 7
Re: Yellow too high on GRACoL 7
- Subject: Re: Yellow too high on GRACoL 7
- From: Bret Hesler <email@hidden>
- Date: Fri, 07 Apr 2006 10:42:49 -0400
- Thread-topic: Yellow too high on GRACoL 7
There are several problems with OB. There are several fluorescent dyes that
are used in paper making, and they react differently to UV light. Also, they
do not have a linear response to the intensity of the UV. This makes it hard
to predict the response in a light booth with one level of UV with a spectro
with a different level of UV. Also, pulsed xenon powered spectros will
excite the Obs differently than tungsten, and an Xrite UV filtered spectro
will read differently from a Gretag UV filtered spectro.
Another problem is that, being dyes, they are impermanent. I had fade tests
done on some papers with optical brighteners. They burn out very quickly in
sunlight. Approximately 2 weeks of summer sunlight will just about
completely burn them. I have seen yellowing on the edges of test sheets that
have been stacked in a view booth for a month or two.
I believe I heard D50 is being changed with less or no UV, and the light
booth manufacturers are removing UV from the bulbs, which will make OB rich
paper less bright and blue in a view booth. That kills the effect, but will
that matter to the design community, which wants brighter and whiter papers?
Bret Hesler
L.P. Thebault Company
> I can't remember the exact instrument model and make but, like Roberto
> pointed out, the paper manufacturing industry has long developped the means
> of assessing the level of OB in paper. How else could they control their
> manufacturing? It's not like the technology or science is not there, Steve.
> It may be that it's not readily available for mere eathlings like us. But I
> don't see how IdeaAlliance and Gracol could not take the lead with this
> issue. Unless they don't want to open up a large can of worms...
>
> Roger Breton | Laval, Canada | email@hidden
> http://pages.infinit.net/graxx
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