Re: monitor uniformity questions
Re: monitor uniformity questions
- Subject: Re: monitor uniformity questions
- From: "dpascale" <email@hidden>
- Date: Sun, 17 Aug 2008 16:02:57 -0400
Hello Allen,
Welcome to the list!
i1Pro and i1Share, although looking around today I see that Babelcolor may
be a better software for this. (With i1 I had to use the ambient light
mode
without the ambient head to measure the screen) I did get readings that
seemed both significant and meaningful.
You should use the "Emission" mode to get calibrated Luminance measurements.
Using the Ambient mode without the diffuser "may" give you relative values,
but the data will not be calibrated (and that causes other problems).
Calibrating the i1 in the "Emission" mode in BabelColor requires a "White
Level" measurement. This white level is fundamental to get proper data.
(This said, the "White Level" does not need to be the display on which the
program runs; it could be another display or even a light box if you measure
transparencies.)
1. Would I really get any better data from Babelcolor? (I might buy it
anyway just because it looks like a cool and useful tool, but I'm getting
a
bit tired taking readings off of this monitor) And what should I really be
measuring; luminance, color temperature, L*a*b* values, all three, or
something else?
BabelColor ISO 3664+ tool will give you luminance, color temperature,
chromaticity error for up to nine positions (located as per ISO 12646), as
well as uniformity data based on the luminance at these 9 positions.
Now, ISO 12646 does not go into the corners; in fact it starts at 1/4 of the
display dimension and stops at 3/4 of the display dimensions.
Display performance in the extreme corners is often less than ideal (except
in high-end displays).
In addition, the ISO 3664 and 12646 standards are relatively conservative
when use against high-end equipment which "should" meet them easily, and
some specs should be met by all LCD displays. For instance, it calls, for a
75 cd/m2 minimal luminance; this was a good number in the CRT days, but many
LCD display user now calibrate at around 160 cd/m2 (if only because they
cannot calibrate their dispplay at lower values!).
You may want to read the BabelColor CT&A Help manual in these sections:
- Spectral tools Graphic Interface/ISO 3664+ tools
- Technical data/Spectral tools description / ISO 3664+ tools dewcription
- Tutorials 8 and 10
2. Should I be expecting any more uniformity from this monitor? Is there
anyone else who has one? And, if so, how uniform does it appear to you?
I get plus or minus 50K variation in uniformity on a 200$ 19 inch display. I
have no experience with the display you mention; however; I suggest you
should redo your measurements in Emission.
Uniformity requirement is that luminance shall be at least 90% of the
central luminance for the positions defined in the standard (not the extreme
corners).
Your 600 lux non-uniformity indicates that you made "Emission" measurements
using the "Ambient" mode (not to be done as mentioned above) since emission
measurements are not in lux but in cd/m2 (also called nits). Again, redo the
measurements in "Emission" mode and the results should be better.
Regards,
Danny Pascale
email@hidden
www.babelcolor.com
----- Original Message -----
From: "Allen Furbeck" <email@hidden>
To: <email@hidden>
Sent: Sunday, August 17, 2008 2:15 PM
Subject: monitor uniformity questions
Hi folks, Since this is my first post, perhaps I should introduce myself.
My
name is Allen Furbeck, and I just completed a master's program in digital
photography at The School of Visual Arts here in NYC. Chris Murphy taught
the color management class, and Andrew Rodney was kind enough to do a
guest
lecture for us. I've been lurking here since Chris recommended the list to
me about 8 months ago, but as I said this is my first post. My color
science
skills are probably intermediate at best, but I have been both painting
and
making photographs for 30 years, and have a pretty good eye for color and
the issues that it raises.
I just bought a NEC 2490 w/spectravision software, and in general I like
the
monitor, but I'm a bit iffy as to whether I should be expecting more color
and tonal uniformity across the screen. Visually, it is clearly both bluer
and
darker moving from the center of the panel to its corners. The monitor has
an adjustment in the OSM called colorcomp which compensates for this and
does a fairly good job especially with tonal variation. (Does anyone know
how this adjustment works? It seems a bit like black magic to me) There is
still, however, a noticeable amount of variation especially in the
corners,
and especially with an all white screen. I tried measuring this with an
i1Pro and i1Share, although looking around today I see that Babelcolor may
be a better software for this. (With i1 I had to use the ambient light
mode
without the ambient head to measure the screen) I did get readings that
seemed both significant and meaningful. There was a variation of as much
as
300 lux and 300 degrees K with colorcomp on, and as much as 600 lux and
800
degrees K with it off. The variations from multiple measurements at one
source point were usually less than a couple of lux or within a range of
about 20-30 degrees K.
So my questions are:
1. Would I really get any better data from Babelcolor? (I might buy it
anyway just because it looks like a cool and useful tool, but I'm getting
a
bit tired taking readings off of this monitor) And what should I really be
measuring; luminance, color temperature, L*a*b* values, all three, or
something else?
2. Should I be expecting any more uniformity from this monitor? Is there
anyone else who has one? And, if so, how uniform does it appear to you?
Thanks in advance for any advice you might have,
Allen Furbeck
--
Allen Furbeck
508-526 West 26th Street, Studio 7D
NY, NY 10011
212 807 7594
allenfurbeck.com
email@hidden
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