Re: Dreamy picture (Dreamcolor monitor)
Re: Dreamy picture (Dreamcolor monitor)
- Subject: Re: Dreamy picture (Dreamcolor monitor)
- From: Klaus Karcher <email@hidden>
- Date: Tue, 21 Oct 2008 19:16:26 +0200
Hi Roger et al.,
Klaus Karcher wrote:
Roger Breton wrote:
Are you going to have some time (?) to quantify its uniformity? Maybe
something along the SWOP's new monitor requirents? See BabelColor's
CT&A ISO 12646 targets here :
http://babelcolor.com/main_level/screen_shots/Spectral_Tools_ISO2.htm
Maybe the UDACT software also does this?
The UDACT uniformity test uses 9 patches and 3 luminance levels (I guess
it also uses the ISO 12646 brightness target). The maximum deviation for
the luminance is 10% from the center to the 8 points around. It also
calculates Delta C, but the result is only informative. I don't have the
UDACT software, but I guess that even the old panel would have passed
the test: I measured 11% luminance deviation and Delta C 6.9 *between
the two most objectionable spots*. The uniformity according to the UDACT
tool would have been certainly better as none of the spots exactly met
the UDACT measurement points.
In matters of uniformity the new HP Dreamcolor panel clearly beats
every other wide gamut display I've seen so far (and I've seen
almost all available models). It is at least as uniform as the
"narrow-gamut" EIZO CG210 and much better than the newer EIZO
"Digital Uniformity Equalizer" models (CG211, CG221, CG241).
Much better? I would like to believe your subjective judgement,
Klaus.
And it comes back to my above suggestion of using the ISO-12646
target to quantify its uniformity in terms of luminance and
chromaticities.
I'd be interested to compare with the Eizo CG21 I have here (I won't
dare show the figures for my Samsung...).
I'll take some measurements next week and will report on the results.
here are my results:
max. luminance deviation CG210:
9.2 +/- 0.4% (on 95% confidence level)
max. luminance deviation HP Dreamcolor:
4.1 +/- 0.4% (on 95% confidence level)
(max. acceptable luminance deviation according to UDACT report: 10%)
I tried to follow the UDACT method, whereas my only source of
Information is a UDACT report I got: I have neither the UDACT software
nor BabelColor nor the ISO 12646.
I measured my screens at the same relative locations as those shown in
the ISO 12646 screenshot on BabelColor's website (scaled and stretched
to full screen size) at 3 luminance levels (100%, approx. 20% and 3%)
and averaged 5 measurements per location and luminance level. I used
Argyll spotread -s -d -H and an eye-one pro to measure. I moved the
device slightly after each measurement. Then I averaged the results and
calculated the luminance deviation in % from the center to the 8
measuring points around it.
Nevertheless I think the results should be taken with a pinch of salt: I
guess evaluating the uniformity based on 9 locations and measured with
an eye-one pro can as well mean measuring the cleanness of the screen,
its pressure sensitivity, the shakiness of the operators hand or the
polarization properties of the screen and measurement device ;-): One
has to turn the eye-one and measure freehand or has to remove the panel
from the base to position it horizontally to measure the lower row.
In other (i.e. German engineer's) words: "Wer misst misst Mist" :-)
A more meaningful yet relative and subjective evaluation of uniformity
can IMHO be carried out simply by eye (on different levels of uniform
gray). And my subjective sensation tells me that that both screens are
very uniform and my HP Dreamcolor is *slightly* better than my EIZO
CG210 -- but it is not "more than twice as good" (that's what the
measurement results imply).
Klaus
--
Klaus Karcher * Eichenallee 18
26203 Wardenburg * Germany
Tel. +49 441 8859770
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