Re: Posterization in a Press Profile?
Re: Posterization in a Press Profile?
- Subject: Re: Posterization in a Press Profile?
- From: Mike Strickler <email@hidden>
- Date: Wed, 30 Sep 2009 14:11:08 -0700
I second all of Terry's and Roger's remarks while adding that
posterization itself is, in my experience, is usually indicative of a
real measurement error, that is, some of the wrong patches being
measured, rather than just having a less than ideally printed chart.
I once had a striking example of this when a customer of a photo lab
called to complain that the sand in his sunset beach images had
turned pee-yellow after converting to our profile. No anomalies were
visible in any of my test images, but when I used the customer's
image I indeed saw the problem. What had apparently happened is that
my Spectroscan had gotten ever so slightly off track so that it
wandered over the border and partially measured one or two wrong
patches. This was really insidious because it wasn't obvious. The
EyeOne is a much better instrument than some here are giving it
credit for, but it is positioned and propelled by hand, and so the
angle of the head to the paper may vary more than it should. This may
be part of your problem, and for this reason you might consider
getting ahold of a more automated spectro as as a DTP70, iSiS,
Spectroscan, etc.
At the risk of tedium I will repeat my colleagues' caveat: Please do
be careful when characterizing a device as drifty as a press. It is
not a trivial exercise to get truly representative and useful
measurements, and what you do get will need to be averaged and
"smoothed" to be make it more generally valid over time. This is not
a procedure that most in-house personnel take on, and you may wish to
call on some outside professional assistance here.
Good luck,
Mike
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