Re: Media Testing for maclife.de
Re: Media Testing for maclife.de
- Subject: Re: Media Testing for maclife.de
- From: Uli Zappe <email@hidden>
- Date: Mon, 15 Sep 2008 17:01:21 +0200
Am 15.09.2008 um 07:30 schrieb Eric Chan:
I'm a bit at odds with the scene-referred/output-referred
distinction for theoretical reasons and prefer to think in process
chains. For my evaluation, I'm taking the "earliest" result a user
can get hold of in a specific process chain.
It's a very important distinction, because it comes down to what
you're trying to evaluate.
I'm not denying that it is important how close the profiling process
can approach the "raw device", but that's not different from profiling
a printer, a scanner or a display.
What I'm at odds with is the terminology ("scene" and "output"),
because it is misleading (a working space like ProPhoto, which was
obviously designed with input devices, not output devices in mind,
would still be categorized as "output-referred"), suggests a duality
where there are actually multiple processing stages, and seems to
imply a specific aesthetic theory (the goal of images is to please).
If you're doing scene-referred colorimetric evaluation, then this is
much more in line with "what the camera sees" because everything is
still linear. The evaluation needs to be done on the linear data,
which is rarely done by the home user because it can be very
difficult (sometimes impossible) to get the linear data out of the
raw converter. (Most of the difficulty comes from the fact that, if
such an option exists, it's not documented; Camera Raw falls into
this camp.)
As far as my *evaluation* is concerned, I already tried to point that
what I'm evaluating are process chains, i.e. complete "packages" that
are offered to the user. How you characterize these packages depends
on the package, but most would certainly be labelled as "output-
referred" by you. I'm not so sure in the case of Capture One PRO where
the output TIFF is still in the camera color space as described by the
assigned ICC camera profile that Phase One uses.
In your terminology, is this still scene-referred (still original
camera color space) or already output-referred (white balance and tone
curve set)?
In my view, doing output-referred evaluation is more practical in
terms of studying whether the output is pleasing or useful to the
user, but is much farther removed from the camera because it is
subject to non-linearities introduced by the raw converter (almost
always a strong brightening tone curve, and a bit of an S curve).
As far as *profiling* is concerned, clearly the best approach would be
the one that gets closest to the device. However, note that even
ProfileMaker (hardly an application for "home users") requires a
target TIFF with white balance and tone curve already set, or else it
won't work.
Where did you get the reference patch values for the SG chart?
From the accompanying reference file. But I additionally validated
these values with my reference i1Pro (mean deltaE(1976) ~0.3).
Bye
Uli
________________________________________________________
Uli Zappe, Solmsstraße 5, D-65189 Wiesbaden, Germany
http://www.ritual.org
Fon: +49-700-ULIZAPPE
Fax: +49-700-ZAPPEFAX
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