Re: Epson canned profiles
Re: Epson canned profiles
- Subject: Re: Epson canned profiles
- From: ben <email@hidden>
- Date: Mon, 16 Apr 2018 11:03:43 -0700
On Apr 16, 2018, at 10:18 AM, Andrew Rodney <email@hidden> wrote:
> THREE different settings in the print driver to make 918 color patches.
Just to make sure I'm understanding your workflow...you have a 306-patch chart
that you print three different ways? And then you read each chart
independently, merge all samples into a single results file with 918 samples,
and generate your profile from that?
(Seems weird and highly questionable without some solid colorimetric data to
back up such an approach...so either you've got that sort of data or I'm
misunderstanding your workflow or your workflow is invalid.)
> 5000 patches, the average dE was 0.5!
Yes, that's maybe a tenth or two of a dE better than what Argyll generates on
an iPF 8100 with similar-sized charts.
But you're still not even pretending to answer some really, really basic
questions.
You've told us how tight a fit your profiles are to the measurements you've
made, which is probably good. (It's possible to over-fit to the detriment of
profile quality...probably not a problem with a thousand-patch chart on a
modern printer, but a decade ago I would very much have suspected over-fitting
with the numbers you supplied. And, if you really are only sampling a few
hundred locations in the printer's color space, I'd definitely start to suspect
over-fitting -- especially since the triple redundancy may well trick the
profiling engine into over-emphasizing those locations.)
But I'm asking a trivial question completely unrelated to profile fit.
What, exactly, in D50 L*a*b*, is the darkest color the printer generates with
the most economical setting? And what does it generate with the highest quality
setting?
You've got your just-printed chart there in front of you, right? And you just
measured it, no?
Unless you're doing something utterly bizarre, at least one of the patches on
that chart will be R=G=B=0.
All you have to do to answer this very simple question from me is find that
patch in your measurements, once for the one setting and another for the other
setting, and report what the measured D50 L*a*b* (or XYZ or other absolute
coordinate system) values are.
Is it really so hard for you to understand what I'm asking for? Really so hard
to answer it? Really so hard to understand why it might matter? Really so hard
to believe that, whatever Epson is doing today, it's been a source of challenge
in the past?
I mean, it seems like not that long ago that forum posts were about nothing but
printer dMAX this, dMAX that -- obsessing over which made the darkest blacks,
which ones were problematic because the lowest L* colors they could print were
so far off the neutral axis, and so on. Sure, technology has improved
dramatically...but do you really expect us to take your perfectly unremarkable
error fit report as evidence that Epson's dMAX is the same regardless of driver
settings?
...er...you _do_ know what that error report is, right? You supply your
profiling engine with the RGB values you printed and the L*a*b* (etc.) values
you measured from the print. The engine builds an ICC profile that maps
requested L*a*b* values to RGB values to send to the printer. Your report is
the result of taking your measured L*a*b* values, running them through the
profile, seeing what RGB values the profile generates, and comparing them with
the actual RGB values you sent to the printer. In other words, all you've done
is tell us how tightly your profiling engine was able to fit the profile to the
measurements; you haven't told us anything about the measurements themselves....
Cheers,
b&
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