Re: Ooops - D65 != D65 ???
Re: Ooops - D65 != D65 ???
- Subject: Re: Ooops - D65 != D65 ???
- From: Uli Zappe <email@hidden>
- Date: Thu, 21 Jun 2007 01:05:40 +0200
Am 20.06.2007 um 19:50 schrieb Andrew Rodney:
On 6/20/07 10:37 AM, "Robin Myers" wrote:
Since the instruments are agreeing with each other with respect to
the native white point measurement, other places to look for the
error in your D65 settings are in the various software packages
I suspect that's the big black hole here. The practice of color
management
would indeed be interesting if the same values measured produced
the same
results in a final profile (or when ink hits the paper). Doesn't
seem close
to being that perfect world.
Yep, that's really my impression, too.
To make the implicit question pointed:
It's easy to agree that color management should be used in the sense
that ICC profiles should be used; but if there's such a variance
between the profiles generated by partly really expensive devices,
why not simply stick to the factory profiles that hardly would be of
bigger variance and deviation from the ideal? (I'm aware that
profiling is much more than setting the whitepoint; I just want to
make the point clear with this example.)
Asking myself this question, I thought it could be interesting to
compare the profiles I created to Apple's default profile for my
display, and for profiles that can be derived from that with visual
tools like Apple's Calibration Assistant.
In this context, I also found that Apple lists the native whitepoint
and gamma of my Cinema display in the Calibration assistant. Since
theses can't be values that Calibration Assistant actually measures
(it doesn't measure anything), I assume these are theoretical values
from Apple's database for my type of display. This, of course, makes
it interesting to compare these theoretical values with what my
measurements with Spyder revealed.
Display data according to Apple's Calibration Assistant (not measured
data):
native white point: 0.313 0.331 6420 K
Data measured with Spyder (copied from earlier mail):
uncalibrated: 0.311 0.338
Eye-One Display native: 0.309 0.337
Eye-One Pro native: 0.310 0.337
Spyder2Pro native: 0.310 0.337
So the x value seems to be close to the theoretical value, the y
value a bit more off from the theoretical value - whatever the
relevance of this. Higher y value means a greenish shade, and my
Cinema Display actually looks quite greenish when used with a native
whitepoint, so the Spyder might be more correct than Apple's factory
data.
But anyway, here are the new profiles, as measured by Spyder:
Apple factory profile: 0.308 0.335
Calibration Assistant D65: 0.308 0.333
So if you include both these profiles into Robin's comparison, you get:
x y dx dy
D65 Target 0.313 0.329
i1 Display 0.315 0.341 +0.002 +0.012
i1 Pro 0.314 0.333 +0.001 +0.004
Huey 0.307 0.328 -0.006 -0.001
Spyder2Pro 0.313 0.325 0.000 -0.004
Apple factory profile 0.308 0.335 -0.005 +0.006
Calibration Assistant 0.308 0.333 -0.005 +0.004
So if you create a ranking list by adding the absolute values of dx
and dy, you get:
1. Spyder2Pro (0.004)
2. i1 Pro (0.005)
3. huey (0.007)
4. Calibration Assistant (0.009)
5. Apple factory profile (0.011)
6. i1 Display (0.014)
(but note that measurements were made with the Spyder, so the first
place for the Spyder itself seems logical and isn't "objective")
So at least, this tentative experiment would still argue that
profiles created by measurement devices are mostly better than other
profiles. :-) (Don't take this too serious, please - it's not a
scientific result, rather an encouragement that dealing with color
management devices might make sense, after all ;-) )
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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