[argyllcms] Re: NEC monitor controls

Hi Volker and All,

I just replaced my aging Dell Trinitron (could no longer get anywhere near a useable black point) with a NEC LCD2190uxi and have the same questions as you. Here's what I've come up with so far and hopefully someone who knows better will point both of us in the right direction.

Poking around the argyll mailing list I found the following:

http://www.freelists.org/archives/argyllcms/01-2008/msg00115.html, Graeme Gill says:

If you
want to minimize artefacts on an LCD you want to
set the contrast and white points to their native
values (ie. where the monitor is not manipulating
the digital signal levels). It may not be easy
to figure out what this is. In this scenario
you would probably only want calibration to
set the transfer characteristic and neutral
axis, and leave the white point native.

Based on the above quote, I used the following settings/options when I calibrated/profiled:

dvi connector (in digital not analog mode)
Sharpness 26.2 (factory default - I seem to recall "Will" from nec in a dpreview posting said use factory default)
Contrast 50% (default)
Black level 128 with r=g=b=0 (defaults)
Colorcomp: It doesn't seem to make much difference whether it is on or off - the screen is brighter with colorcomp off, but I don't see any difference in evenness of lighting across the screen. Brightness recommendations seem to be: what is comfortable, near ambient light levels, or what matches my print-proofing light, in any case probably somewhere in the neighborhood of 100-150 cm/m, as measured by Argyll/spyder2. I have the Brightness set at 51.4%, measuring around 110 cm/m according to Argyll/Spyder2.
Color Control (temperature) = "native"
Gamma Selection= "NON" "No Correction"

I think the native color temperature of the 2190 is 5800K. Based on your email, the 2190 has the same color-temp presets as the LCD1990. I did some experimenting with the on-screen monitor color temperature settings and found that the RGB numbers (as shown by the monitor on-screen controls) for temperature=5800K are R=231 G=231 B=228. For all other temperatures the RGB numbers are progressively farther apart from one another. The only difference I can see between "native" and "5800K" is that 5800K is a little less bright. Moving the on-screen r,g,b monitor temperature colors all to 255 looks "just like native". The sRGB option looks bluer by comparison (as it should, given that sRGB has a temp of 6500K). If I understand Graeme, leaving the color temperature at "native" (r=g=b=255) should result in the least unwanted side-effects, unless the NEC lcds really aren't compromised by messing with their defaults. I plan on calling NEC and asking, but who knows how valid the answer will be.

When I set the monitor on-screen Gamma Selection to NON and measure the gamma using:
dispcal -v5 -p 0.5,0.05,2.25 -yl -R
I get
Uncalibrated response:
Black level = 0.53 cd/m^2
White level = 110.88 cd/m^2
Aprox. gamma = 2.24
Contrast ratio = 208:1
White chromaticity coordinates 0.3276, 0.3282
White    Correlated Color Temperature = 5732K, DE to locus =  6.3
White Correlated Daylight Temperature = 5734K, DE to locus =  9.8
White        Visual Color Temperature = 5935K, DE to locus =  6.0
White     Visual Daylight Temperature = 6098K, DE to locus =  9.5
Effective LUT entry depth seems to be 8 bits

When I set the Gamma Selection to 2.2 and measure the gamma I get "Aprox. gamma = 2.10". Setting the monitor gamma to 2.4 results in a measured gamma of 2.30. Setting the monitor gamma to 2.5 results in a measured gamma of 2.40.

So which gamma setting would be recommended for calibration/profiling? NON or 2.5? I used NON, but I think 2.5 might be better. I did a calibration/profile using:

/usr/local/argyll101/bin/dispcal -v5 -p 0.5,0.05,2.25 -yl -qh -o necnativenon

with the monitor gamma set to "NON" and all other settings as above. But perhaps I should redo the calibration? Also, in the Argyll documentation Graeme mentions that for some purposes just profiling without calibrating might be preferable, but I wasn't able to decipher when or why.

FWIW, I loaded the calibration produced by the settings given above and set the profile as the system default using dispwin. I copied "necnativenon.icc" to a shared folder and thence to the /colors folder in my VirtualBox W2K installation and made it the virtual W2K display default. I also pointed gimp 2.4 under linux to the same monitor profile (using relative colorimetric). To my amazement test images on pshop under W2K in the VM actually completely matched the same images viewed by gimp 2.4 under Linux. Digikam 0.9.3's "showfoto" (with appropriate fiddling - nothing "CM" related is straightforward with digikam) also matched. (Linux Krita, Linux Firefox 3, and a couple of other windows imaging programs all have an "issue" - seems to be the same issue, but that is a topic for another post - not even sure if the topic is appropriate for this mailing list.) I found the following test images to be very useful when checking my calibration/profile/application settings: standard "printer" test images from here: http://www.normankoren.com/makingfineprints1A.html#TestPrint,
plus the images here:
http://www.oceanlight.com/html/about_color.html for showing issues with the darker greys
and here:
http://www.clarkvision.com/galleries/gallery.africa/web/ndutu.night.rnclark.c01.2 for showing color casts (the wrong settings easily push the tree trunks from yellowish to orangish and the foliage from green to yellow-green) and also any failure to differentiate among the darker tones.

Elle

And I hope I posted correctly this time!



Volker Sauer wrote:
Hi,

as you might know from one of my last mails, I'm using two NEC
Multisync LCD1990FXp to do my work.
These monitors are capable of displaying the whole sRBG gammut (even a
little more tha this for red and green values) and offer some controls, that other displays don't have.
My problem is, that I can't match those controls to the settings I need
to adjust before calibration. Maybe you could help me out, which setting
means which parameter in dispcal:

- Brightness
- Contrast
- Black-Point
- Color-Temp (Settings can be: * sRBG (6500k) (which I use)
        * original colors (means native colors of the LCD)
        * several presets (9300, 8200, 7500)
        * or RBG-Settings for each channel

The latter (Color-Temp) is clear.
But how do I use Brightness,  Contrast and Black-Point for adjusting?

Regards
Volker



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