[argyllcms] Re: Calibrator correction for Eye One Display 2 & GB-LED Backlight LCD Monitor?

  • From: "Al Robertson" <akr0912@xxxxxxxxx>
  • To: <argyllcms@xxxxxxxxxxxxx>
  • Date: Thu, 5 Sep 2013 18:50:43 -0400

Dear Graeme,

Thank you very much for your detailed reply. I appreciate your time.  

Good news - I found a lab at work willing to lend me an i1Pro.  I'll order
the monitor now that I have a plan to calibrate it.  I can calibrate it once
with the i1Pro, and also create a colorimeter correction for my specific
i1D2. Then I can calibrate it with the i1D2 and compare the result with the
first calibration to confirm the accuracy of  the new correction file. This
seems to offer a good  chance of success.

Best regards,
Al

-----Original Message-----
From: argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-bounce@xxxxxxxxxxxxx]
On Behalf Of Graeme Gill
Sent: Wednesday, September 4, 2013 10:51 PM
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Re: Calibrator correction for Eye One Display 2 &
GB-LED Backlight LCD Monitor?

Al Robertson wrote:

Hi,

> The NEC has become dim over time and I'm looking to replace it soon 
> with an Asus ProArt PA249Q which, like the better known Dell U2413, 
> has the LG
> LM240WU9-SLA1 AH-IPS panel. But I have one problem.

> This relatively new panel has a GB-LED backlight (improved gamut), but 
> from what I've read, the curves are sufficiently different that I 
> would need to either go buy a new calibrator (X-Rite wanted to sell me 
> the i1Display Pro - $229), or get a new correction matrix to 
> successfully use my existing colorimeter.

The i1Display Pro is a pretty solid instrument, and well worth the
investment.

> Does anyone have a corrections file for the Eye One Display 2 and a 
> GB-LED backlight display? Or perhaps be thinking about either making 
> one, or including GB-LED support into argyllCMS/dispcalGUI as a new mode?

The variability of the instrument is such that I'd be a bit suspicious of a
correction matrix made for a different instance of the i1d2.

> If not, any ideas on how to make or fake one at home?

The best way of course is to use a spectrometer (ie. i1pro or ColorMunki
spectro.) as a reference on your display against your i1d2.

> One idea.The monitor claims  to come factory calibrated within 3 delta 
> E (fingers crossed.) Is there at least a way to make a correction file 
> that uses the factory calibration as a trusted baseline so I can 
> always get back to that even if the colors drift over time (or if I 
> want to customize the calibration)?

OK, here's an outline of how you might go about this. I'm leaving out some
details, and I haven't actually tried it, so you may well need to
troubleshoot the procedure:

Create a reference test set of (say) a 3^3 or 4^3 cube set using targen, ie.
something like:

    targen -v -d3 -e0 -B0 -m3 -f0 test

Copy this to a reference set:

    copy test.ti1 ref.ti1

Set your new display to (say) sRGB mode, and measure the test set with your
instrument.

    dispread -v -yl test

Create a reference set using the sRGB.icm file, that we assume the new
display is calibrated to:

    fakeread -v sRGB.icm ref

A problem with this is that the real readings will be returned to absolute
values (cd/m^2), whereas the fakeread values are normalised to 100, so we
will have to make sure that the fakeread values get scaled the same way.

Open the test.ti3 file in a text editor and copy the
LUMINANCE_XYZ_CDM2 line, ie. for the sake of an example:

  LUMINANCE_XYZ_CDM2 "46.509281 49.445099 45.615122"

into the ref.ti3 file in a similar position. This should cause the values to
be scaled to match the instrument values.

Create a ccmx correction matrix from the ref and test results:

    ccxxmake -v -f ref.ti3,test.ti3 correction.ccmx

You can then use the correction matrix with your instrument on that display,
ie.

    dispread -yl -X correction.ccmx etc.

Graeme Gill.



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