Re: Colorsync-users Digest, Vol 5, Issue 133
Re: Colorsync-users Digest, Vol 5, Issue 133
- Subject: Re: Colorsync-users Digest, Vol 5, Issue 133
- From: Mike Strickler <email@hidden>
- Date: Tue, 22 Apr 2008 10:52:08 -0700
The second one has now surfaced:
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Message: 3
Date: Mon, 21 Apr 2008 21:24:12 -0400
From: Terence Wyse <email@hidden>
Subject: Re: Photographers, printers, and proofs
To: "'colorsync-users?lists.apple.com' List"
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Message-ID: <email@hidden>
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On Apr 21, 2008, at 8:59 PM, Mike Strickler wrote:
No I'm not saying that, I'm saying "ideally most of the values in
12647-7 should be around half or or even a third of the tolerances
at calibration time. This will give the system room to maneuver
while still being within the defined MAXIMUM tolerances set forth
by ISO".
Yes, that sounds about right. But let's also keep the bigger picture
in mind: The standard defines an "average" reference press/paper
combination, and in the area of paper white alone it's quite easy to
be off the standard 95 0 2 #1 sheet when proofing accurately for the
actual press stock. In that case one must either be a little more
tolerant or actually proof to a custom standard to allow for the
different white point.
I think you meant a standard paper white of 95 0 -2 (ISO Paper Type 1
and 2).
Absolutely, -2. Which is a bit bluish, a compromise between various
substrates used, including some REALLY bluish ones.
Rather than proof to a *custom* standard to allow for the different
paper white, I think what you'd want to do is set the proofer up using
a standard data set such as GRACoL2006_Coated1 or FOGRA39 for example.
That way, the paper white on the proof will be correct, assuming
you're allowing the proofer to simulate/tint the paper white. Better
yet, find an inkjet media that matches the spec exactly and you won't
have to worry about it. I can't remember the last time I was asked to
profile to a non-standard data set (OK, it was last week on a customer
Fuji FinalProof!). The norm these days seems to be to use standardized
data sets/profiles and I think that's a good thing.
I agree, BUT we know there are some complications. If the proofing
stock is right around 95-96 L*, for example, and you're asked to
proof to reference quite different from FOGRA/GRACoL in the a and/or
b value (in other words, hue), an absolute conversion will lay down
enough ink in the background (to correct the paper hue) that the new
whitepoint will be too low in the L*--too dark. You'll also have
problems judging minimum dot visually. So either you loosen the
expectations on DeltaE, especially on paper white, or you use
relative, which is less accurate again, or you adjust your reference
(and don't call it FOGRA, GraCol, etc.). There's no one "correct"
answer, but it's something to be discussed with the client and dealt
with.
As far as your original post, I may have read it the same way Thomas
did that you were arguing for a LOOSER tolerance than ISO 12647-7
specifies. You seemed to be saying that the tolerances were too tight
and not practical for production proofing. I'd argue the opposite.
So would I, if we're talking about an average of 3.0, which is ISO
for production.
I
set up production proofers all the time that can EASILY maintain the
specified tolerance. In terms of actual dE numbers (I know, dE isn't
EVERYTHING but it does give us something quantifiable) its becoming
almost routine for me to see systems, both Epson and HP "z", to get
under .30 dE average with no patches greater than about 3 dE compared
to the standard data set they were intended to match.
Assuming this is DeltaE abs, not 2000, that is very low. Now we'll do
an A-B and see if you can tell the difference between .3 and, say, .7
when the charts are switched.
In fact, the
last HP Z2100 I did was a bit under .20 dE with ZERO patches over 2
dE. You can choose not to believe that but it does happen...and I'm
not trying to scare anybody! :-)
Of course you are... As you can see, the thing I object to in these
threads is the flogging of tiny differences in Delta E numbers in
order to sell services, printers, and RIPs. It reminds me of guys
standing on a street corner and comparing horsepower of cars, as well
as other single numbers. It's bad science and pretty unsubtle
salesmanship. Sorry if that seems brusque, but that's how it's
consistently appeared.
As far as calibration tolerances, I'm starting to lean towards .50 dE
avg. and 2 dE max dE for production tolerances and so for that seems
pretty reasonable (that's for HP Z printers, I find Epsons to be a bit
less tolerant needing about .75 dE avg. and 3 dE max for normal
production variation). Point being, with today's printers and GOOD
proofing RIP software with a fundamentally sound calibration and
profiling process, we should expect much TIGHTER tolerance than what
ISO 12747-7 specifies.
I think those numbers are unreasonable for the Epson unless regular
recalibrations are performed. Especially when we see a bump of DeltaE
1 or more with a change in paper or ink cartridge.
Look, a system can be optimized to a particular reference (assuming
especially with a RIP that does iterative Lab optimization) to very
low DeltaEs, but this is to some degree dependent on which reference
it is. Paper is still an issue, and a numerically perfect proof may
be visually unacceptable to the customer. A laminate proofer
addresses this pretty well, but it won't give the super-wow numbers
you're floggong--though it may perfectly fit the customer's needs
(no, I don't sell laminate proofers). And that's my point. There are
a lot of factors to consider when on the actual client site. Just
peddling a solution based on a tiny DeltaE in one ideal case can
badly miss the mark for that customer. The REAL optimization problem
is meeting as many of the customer's needs as possible without
failing on any one objective, keeping the cost reasonable, and the
training and maintenance issues within practical limits. I assume
that's what you guys are doing and doing well; it would be great to
see THAT sense reflected in discussions of proofing. Then we might
get more participants.
Thanks.
Mike
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