Re: Real world experience w/ GMG and Oris RIPs
Re: Real world experience w/ GMG and Oris RIPs
- Subject: Re: Real world experience w/ GMG and Oris RIPs
- From: Troy Buccini <email@hidden>
- Date: Wed, 24 Nov 2004 21:46:50 -0600
I just wanted to add a few comments on this discussion as I think we
have a great deal to gain from this topic. I can't speak for GMG as I
have never used it, but I have used Color Tuner since before it offered
iterative calibration and color-matching. I have on more than one
occasion presented two proofs to a customer: One with Auto Color-Match
and the other with just ICC profiles built from a custom extended
version of the ECI and the customer and I agreed that the best visual
match was with ICC profiles.
One thing that always seems to surprise me is that even with 3 rounds
of Color-matching my paper simulation still needs editing. In an ICC
workflow I just load the Ink-jet profile in GMB Color-Picker and do a
spot read of the reference paper white and hit minimize and take those
CMYK numbers into GMB ProfileEditor and use them in Workflow White
Point and save the edited profile. I am usually dead on. And now with
GMB 5 I can edit the k-point to get me a few L* darker.
Please don't get me wrong, I am not bashing the iterative process. In
fact the iterative calibration is very nice. I am however convinced
that using a large custom target will yield as good results and many
times better visual match than running an iterative smaller target
multiple times.
As for GMG not using duplicate patches in the ECI target, That could
really hurt you if your profiling a press sheet. This concerns me...Can
you average measurements?
Well its getting late, have a good Holiday.
Troy
On Nov 24, 2004, at 8:41 PM, Mike Eddington wrote:
Thanks for the reply Graeme. So the issue isn't whether or not we get
better results with GMG, but rather whether it is due to the iterative
process or some other feature that GMG implements.
A profile is not really a curve, it is a mapping in 4D space to 3D
(so it
could be considered a hyper-surface). So no curve can really show you
what's happening between measurement points.
noted...but I can also add fulcrum's to the profile. The CMYK value
that is infered is proportional to the values above and below it,
wouldn't this indicate that colors between patches are being
addressed, or no? Furthermore if a fulcrum is added after the initial
profile creation its value is different than if it is added after
iterations, so there is some interpolation going on.
This is not a valid test. You need to use a verification chart with
test points that are unrelated to the IT8 test values used to create
the profile.
Ok, that makes sense. Is there an existing chart that you would
recommend for this or would a chart, say one that has absolutely no
patches that occur in the It8 (or ECI) or would a 7000 patch chart
created from MeasureTool Testchart Generator suffice?
If one were to go about this, the test chart would have to be printed
off the target device, and then off the proofer using both a GMG
iterative profile and a GMG non-iterative profile (both previously
created with an It8 ir ECI). Then a target to proof comparison made to
verify if there is improvement in measurements of patches of the
iterative proof, correct? Anything I'm missing? Of course if the chart
did contain patches that occur in the It8 or ECI, then there would
definitely be a numerical improvement, if even a slight one.
BTW, I have no idea what voronoi points are. ;-)
mike
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