Schmorp's POD Blog a.k.a. THE RANT
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This document was first published 2020-01-09 07:03:59, and last modified 2020-01-09 13:02:01.

LG 32UD89 info

After replacing my old monitors (two Dell U2711, which were very good monitors if you ask me) by two new LG 32UD89 models (I wanted the LG 32UD99, but obviously that has some nasty design bugs causing it to fail after a year or so), I ran into a few issues. Quality-related.

Issue 1: Wrong EDID

First, the EDID is rather broken - not only does LG give the wrong manufacturing date (month in the week field), it also gives wrong monitor dimensions, obviously taken from the 27" inch model, resulting in wrong DPI settings.

Unfortunately, I found no way to override this via my xorg.conf (neither DPI nor DisplaySize options actually work), so I had to edit the EDID info.

So without further delay, here is the custom LG32UD89.edid I created. It's the original EDID patched to have a display size of 70x39cm and individual mode sizes of 692x392mm, which results in the correct value of 140 dpi. The EDID is for the DisplayPort input and might work less well for other inputs.

Top use it with the proprietary nvidia driver, you have to put this into your Screen section:

 Option         "CustomEDID" "DFP:/etc/X11/LG32UD89.edid"

Where DFP stands for the display device to use - DFP specifically means "all digital flat panels" - if you have another DFP attached, you might want to change this to something more specific such as DFP-2, DP-4 or so.

If you tell me how to do this with other drivers or other operating systems than Unix, drop me a note so I can add it.

Issue 2: Severely Lacking Documentation

The monitors have a gamma setting: you can choose between Mode 1, Mode 2 (the default), Mode 3 and Mode 4. The only bit of info about these in the manual is "choose Mode 4 if you don't need any special gamma setting". Gee, thanks LG.

So I measured the modes with my colorimeter and got these results (the last row is the D65 white point for comparison):

ModeGammaContrastWhite point
Mode 12.01200:10.3112, 0.3185
Mode 22.21163:10.2956, 0.3085
Mode 32.41195:10.3108, 0.3201
Mode 42.21295:10.3049, 0.3204
D650.3127, 0.3290

These values are only guidelines - my right monitor has gamma 2.17 in Mode 4, and my left one has 2.24 (in general, they are surprisingly different for factory-calibrated monitors - my Dell U2711 are practically iderntical even after nearly a decade of different usage).

Based on this, since I wanted my calibration to use D65 and have SRGB-like-gamma, I choose Mode 4 and had to adjust the red channel quite a bit down.