Re: Convert UV-excluded to UV-included
Re: Convert UV-excluded to UV-included
- Subject: Re: Convert UV-excluded to UV-included
- From: Andreas Kraushaar <email@hidden>
- Date: Wed, 23 Dec 2009 08:21:17 +0100
Hi all,
thats why defined viewing conditions are extremely important (the ISO
3664 in the latest 2009 revision takes care of that with a more
stringent UV metamerism index - so a controlled portion of UV light).
However, it is difficult enough to make two papers (with different
amount of OBA) matching there :-)
Since we will start working on that topic soon I would be interested
in your opinion how good the existing "problem categorization" has
been? In other words, do you think the main problems are addressed in
a nice (mutually exclusive, collectively exhaustive) way?
1) printing RGB files on substrates with much OBA (and you don't want
the neutrals (R=G=B) being rendered yellow
2) you have a prima A, e.g. a proof (no or less OBA since you want a
light fast and permanent proof) and a print B, e.g. paper stock with
more/much OBA.
- How do you find out if a match is possible at all?
- What is the best visual technique to modify the proof in order to
get a visual match (under controlled viewing conditions first - such
as a 3664 conforming light booth with adjustable UV).
- What is the best metrology to
a) measure the bispectral reflection (and if that is to much the
spectral radiance factor for the intended viewing condition - what a
telespectroradiometer would measure hitting on it)
b) measure (paper specific) aim values (of whatever kind) to have a
visual match when those values (objectively) match
3) what is a practical method for nowadays graphic arts use cases to
help the printer in adjusting the solid coloration on the press aiming
for an (ISO 12647-2 conforming) print accompanied by a (FOGRA39 or
JanColor or Gracol Proof)
what problem scenarios did I miss?
sincerely
Andy
On 22/12/2009, at 8:40 PM, Mike Strickler wrote:
Any formula you used would be specific to the illuminant and (if
applicable) the reflecting medium. Change illuminants (for example,
going from a spectro with a halogen bulb to one with an UV-included
LED source) and/or papers and your numbers won't be valid. You'll
also find that UV-filtered readings won't match readings taken with
a spectro, like the iSis, that uses for its "filtered" LEDs that
have no (or nearly no) UV component to begin with. The conventional
cutoff filters take out a bit of the visual spectrum as well, so
they result in a more "yellowish" reading in comparison with the
unfiltered reading--how different will depend on how much UV
fluorescence there is in the paper being measured.
------------------------------
Message: 2
Date: Mon, 21 Dec 2009 16:03:18 -0500
From: "Chris McFarling" <email@hidden>
Subject: Convert UV-excluded to UV-included
To: <email@hidden>
Message-ID: <4A752153D4F94EB5BE5AEDAB9A57D263@helo>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=response
I'm wondering if there is formula that exists to convert
measurements from a
UV filtered spectro into data that would simulate that of a non-
filtered
device?
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