Re: Colorsync-users Digest, Vol 4, Issue 393
Re: Colorsync-users Digest, Vol 4, Issue 393
- Subject: Re: Colorsync-users Digest, Vol 4, Issue 393
- From: MSP Graphics <email@hidden>
- Date: Sat, 3 Nov 2007 12:30:55 -0700
------------------------------
Message: 3
Date: Fri, 02 Nov 2007 20:45:23 +0100
From: Klaus Karcher <email@hidden>
Subject: Re: Accuracy of Instruments
To: email@hidden
Message-ID: <email@hidden>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Mike Strickler wrote:
Wait a minute: "In all probability"? The "expert eye"? And "I
guess"?
Would you please be so kind to /not/ truncate quotes beyond
recognition?
Strictly speaking it was a selection, not a truncation, but a telling
one. I guess I'll have to leave your entire post intact (you don't
need to do that with mine)
... but back to the facts:
The University of Wuppertal, the University of applied Sicences
Stuttgart and the FOGRA carried out an investigation about
inter-instrument differences between 8 instruments of 5 manufacturers
and presented the results at the 4. Digitalproof-Forum 2004 in
Stuttgart.
The probes (BCRA tiles, digital proofs and offset prints on APCO
paper)
were measured with a reference instrument before and after the test to
eliminate probes damaged during the test.
They result of the investigation was a Delta E 76 of up to 2 to the
average on 95% confidence level. I think one can argue in good
conscience that these differences are visible and significant in
process
control and quality management.
Klaus Karcher
I understand what you're saying, Klaus, and I agree it sounds
terrible, but two issues occur to me. First, in what practical
scenario should we worry about this--I think Mike E. tries to address
this below--and second, you're raising an an additional issue of
agreement between instruments of different manufacturers and design.
This latter factor may greatly complicate any attempts at
significantly better interinstrument agreement. I do wish we could
hear more from the designers and makers of these instruments because
without that we don't know if what you are asking for is even
possible. In a way, what this whole discussion boils down to is
mistrust and unhappiness with these manufacturers (which now is
mainly just one company). I'm still agnostic on the question: I
haven't seen compelling evidence that they are falling short of their
best effort, given cost and other practical constraints. All that
said, I personally would insist that if there is a requirement of
very close matching of measurements in different locations all the
instruments be of the same make and model and that all had been
recently recertified because we all know that different models/makes
can read quite differently (and think of the different UV-filtering
schemes!) That would go a long way toward cutting down on the sort of
variance you're talking about.
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