Re: New optical brighteners compensation from Xrite
Re: New optical brighteners compensation from Xrite
- Subject: Re: New optical brighteners compensation from Xrite
- From: Marc Levine <email@hidden>
- Date: Tue, 3 Jun 2008 23:44:18 -0400
Well hello list,
I saw this little thread about the new optical brightener stuff from X-
Rite and just had to jump in. Even though I no longer carry the ol' X-
Rite business card, I'm pretty close to the technology and should be
able to esplein.
First of all, this is not simple averaging of 2 data sets (shame on
you Terry.....and you call yourself a scientist!). Also, this is a far
cry from the Optical Brightener Correction that is in PM5. Having been
the product manager for that product, I can say that I am 99.9% sure
that PM5 applies OBC in the perceptual intent - not the others.
Considering that the #1 thing that OBC impacts the most is the
reproduction of paper white (absolute colorimetric), it seems as if
the technology was never able to offer the full value of its potential.
I would also add that - even in its "perceptual form", there was no
real input for this control. You either got it (or at least had the
opportunity to get it) if the software thought you needed it, or
didn't If the software didn't think you needed it. All in all, it
worked (and works) "sufficiently", but is/was not something built to
specifically compensate for the difference between a measured value an
the "visual" value of a color, printed on a media, in a specific
viewing condition.
So what the heck is different about this new OBC thing. For one, it
uses a reference target. Like a color checker. Called a UV checker.
It's kinda like a gray balance card. The key is that it doesn't
fluoresce. What that means is that colors (grays) appear consistent,
relative to the temperature of the viewing illuminant, no matter what
type of UV content your viewing illuminant has. A constant, if you will.
The second interesting point is that the correction is specific. The
workflow entails printing a target, like an ICC target, and measuring
it with the iSis (UV incl+excl). Without giving too much away..... the
software crunches the numbers and comes up with a new target that is
then printed and compared to the checker, visually (because there's
really to way to fully characterize the UV parts of this scenario with
instrumentation that either costs less than $30,000 USD or weighs less
than 30,000 lbs, or both).
So, as you can imagine, the printed patches look somewhat like the
"checker" patches, but vary slightly in color ranging from "this is
how it would look with UVin" to "this is how it would look with
UVout". The user picks the visual match (or matches) and sets the
appropriate params in the software.
At that point, the software will spool up a new set of data for your
profiling pleasure. Then, when using this profile to transform your
image data, you should see a greater similarity between the colors
that the image is supposed to be (what's in the PCS), and what you
visually experience.
Rogers's comment is right on the money about the press sheet - it is a
2 step process. Most high quality sheets have limited brighteners, so
matching them should not be a big deal. For sheets that do have
optical brighteners, you would probably want to run the 2 step process
on the press side. Many times, press setups use 2 runs (1st for plate
curves, 2nd for press char data), and I suppose that - with some
trickery - it could be made to work with no extra "cost".
In any event, it's interesting stuff. If you're working with optically
brightened media....it should be especially so.
Also, for those of you who do not know, I have found a home under the
umbrella of the Color Management Group. Thanks again to all those who
supported me in my short time away.
Best regards,
Marc
--
Marc Levine
Color Management Guy
email@hidden
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