RE: SWOP Proof Certification, TRxxx Characterization Data
RE: SWOP Proof Certification, TRxxx Characterization Data
- Subject: RE: SWOP Proof Certification, TRxxx Characterization Data
- From: Roger Breton <email@hidden>
- Date: Mon, 27 Oct 2008 21:06:49 -0400
Mike,
> I'd consider the targets and tolerances for the ISO 12647-7 colorbar
> to be a work in progress (albeit well overdue).
OK. If you and Todd and Klaus refer to "official" IDEAlliance tolerances on
the ISO-12747-7 Control Strip, I sure don't have an answer for you. True,
Chromix study is expected to throw some light on instrument's variability.
All along, I was under the impression that Klaus was venting his frustration
with regards to what a "certified" IDEAlliance proof was. That is clearly
defined for third party proof suppliers and I don't agree this cannot be
carried on to users in the field. With instrument's quality where they are
today, EyeOnePro's grade and the like, I don't see why adopting these
requirements would create havoc.
I was under the impression that the selection of patches in ISO-12747-7 was
based on some Principle Component Analysis? A statistical procedure that
extracts the most salient feature of a dataset, the most important
dimensions that explains the most variation. I'm sure I remember reading
something to that effect, somewhere. But maybe it wasn't that scientific
after all, more political than scientific. I'll have to look again.
As for variation in instruments for the purpose of forming an independent
judgement about the quality of a proofing system, I confess I come across
some weird cases, cases where the numerical requirements are met within the
IDEAlliance tolerance (the only tolerance I know to use -- good or bad) but,
visually, these proofs bear the distinct fingerprint of the optical
brighteners used in the susbtrate. Meaning, a proof on a b* = -4 appears
decidedly yellowish. And when the client prefers *not* to be offended by
paper simulation, the proof is switched to RelCol and all colors, all of a
sudden, become, well, so distorted visually compared to, say, a GMG or an
ORIS proof. So distorted, in fact, that I wonder why bother with submitting
hardcopy proofs in the first place. This is why I believe press proofing
will make great strides in the coming months, years. At least with press
proofing, there is *no* confusion as what the tolerance is.
> Idealliance's position
> seems to be that the control strip can be used in any number of
> applications/processes, and therefore the best method for determining
> targets is via the B2A tables of a specific profile, and tolerances
> defined between the proof producer and receiver.
I believe you mean the A2B1 table. I don't see how the B2A tables would be
of use here?
OK. Suppose the application/process in question is GRACoL2006_C1. Then what?
One looks up the relevant CIELab values up in either the official TR-00X
dataset or up the relevant ICC profile in Photoshop? And leave the
tolerances between the client and the printer?
So, between ClientA and PrinterA, the tolerance would like not be the same
as between ClientB and PrinterA? That can't be.
> That's just not what
> people expect when they download the colorbar and ponder what to do
> with it, particularly with the inexplicable lack of the
> ISO12647-7_ControlStripV5.txt file.
Boy! The people who download the colorbar and ponder what to do with it
should consult a guys like you, Mike -- I know I would ;-)
> For the SWOP/Gracol Proofing System Certification, to be sure the
> targets and tolerances for proof conformance are well defined, but to
> hold end-users to the same metrics is asking for trouble.
Hope time will tell otherwise.
> Inter-
> instrument agreement is such as to render the ADS tolerances difficult
> to near impossible from location to location.
I'll take your word for it.
> Its certainly a fine
> target for an individual with a static instrument, but as users
> exchange and measure proofs on different instruments, a proof that
> measures within tolerance with one spectro can, and often will,
> measure out of tolerance on another.
Well, this is raising the issue of national lab traceability. For sure, my
SpectroEye refuses to report solid magentas comparably to my 530 or my
Techkon or my ...
I get the picture. But that should not stop us from promoting the use of the
aim points as meaningful targets.
> Another issue is how well a
> smaller number of patches (as the ISO 12647-2) represent conformance
> as compared to the larger patch count IT874....i.e. does a pass toward
> tolerances on one mean a pass on the other?
See my above comment. I remember Don's account of how he said they agonized
over the exact composition of certain patches. The primaries and secondaries
are no brainer to anyone (whether 40% or 50% is another story). The CMY
grays are easy to agree on. But, what do we make of the other patches, you
say? I'm pretty sure I saw some researc, was it was on the Fogra web site?
where there was a graph that showed on one axis the average deltaE between
the MediaWedge and the Reference set (Fogra39L) and the average deltaE
between the 1617 patches of the IT8.7/4 proof and the Reference set on the
other axis, and the statistics used was Pearson Correlation, and it was
clear from the description of the chart that, indeed, the smaller set of the
MediaWedge correlated highly (greater than 90%, if memory serves) with the
larger dataset. Come to think of it, that does not seem like such a hard
procedure to reproduce, as a test, is it?
> With a smaller number of
> patches in the ISO control bar, the answer would be "somtimes". ;)
You and I know that "sometimes" is not good enough with demanding clients.
But we have a clear picture of how to study the relationship.
> I agree that the FOGRA media wedge is much clearer in regards to
> targets and tolerances,
Please forgive my ignorance, Mike but, could you comment briefly in which
ways that is?
> but given the licensing restrictions (and
> rather steep cost),
Yes, horrendous.
> no quite as flexible. Hopefully when the SWOP
> proofing study results are released, there will be action to determine
> more acceptable end-user proofing tolerances
Based on ISO-12647-7 Control Strip, that is?
> (or maybe they would be
> so wide to accommodate instrument variation that the usefulness is
> limited...mike crosses his fingers) .
True, so wide as to render them useless, and we'd be back to square one :(
> Until then, the SWOP ADSs do
> offer some guidance on tolerances,
You would think that the ADS would go as far as defining a metrology
framework including how to measure the target, with what instruments, and so
forth. Didn't X-Rite sold more DTP41's for all the ADS of this world than
any other instrument manufacturer? What about ISO-9001 quality control
programs? Can't we expect people send in their instrument once a year for
re-certification? Wouldn't that lend some credence to ADS? And bring back
some needed inter-instrument agreement?
> but in the end, leaves it to the
> user to define their own.
In one company I work with, they work with each client to verify the
conformity of whatever proofs they dare call "to the numbers"... In the end,
the client decides with its pocket but that does not help the color matching
on press -- there is no free lunch.
> Michael Eddington
Regards / Roger
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden