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LG CX + Calman AutoCal calibration

This post covers my learnings from reading between the lines of too many forum threads, with regard to calibrating the LG CX OLED TV.

My equipment is a 55" LG CX, i1Display Pro colorimeter (Dell OEM 2000 nit edition), i1Pro (v1) spectrophotometer and Calman Home for LG. I have various calibrated monitors to compare to, and enough graphics programming and photography experience to know more-or-less what 'correct' looks like, as well as the many ways things can be subtly incorrect. Also got a couple of factory calibrated monitors and an iPhone SE 2020 (known good accuracy) for sanity checking against.

Firstly, a brain dump of what I have learned: (the actual calibration procedure follows)

  • You need a spectrophotometer. Your results will be worse than stock with a colorimeter alone.
  • With Calman, you don't need to touch the service menu, even to use a non-D65 whitepoint.
  • Never, ever click DCC Reset in Calman.
    • If you have clicked this, you must factory reset your TV or use another picture mode.
    • Resetting a picture mode or performing a 'AV Reset' appears at first to work on the C9 and CX, but as soon as Calman touches that picture mode, the saved 1DLUT is restored. Only a full factory reset (via normal menu, not service menu) deletes it.
  • In real content, I find a good test case for calibration artifacts on these TVs is the effect it has on bokeh. If your eye is drawn to blurred areas and they have a 'digital' quality to them, it ain't right. Look for things like banding and hard edges at the transition into black.
  • Another good test case in real content is to watch an older TV show with dubious levels/gamma (my go-to is Fringe). A scene with naturally but dimly lit faces and solid black behind them is great. Your brain can identify what colours it expects in the gradient across the skin towards black, relative to the well-lit area of the face. A poor calibration will have horrible hard edges and/or transition to an unnatural dark red or grey.
  • For a contrived and reproducible test of calibration artifacts, the best option I could find was plugging in a PC and opening Photoshop, then drawing a radial gradient between 100% and 75% saturation of various colours at the center to black at the outside.
    • Na├»ve Calman AutoCal looked comically bad compared to every LCD monitor I have ever used! Way worse than stock.
    • A radial gradient like this should have a 3D look, and any banding artifacts will remove this effect.
    • A calibration following these guidelines got it looking 90-99% as good as a high-end IPS panel, depending on colour. OLED will never be perfect in this area.
  • For SDR, I can't tell any difference between the input lag of PC mode (setting an input's icon to PC) and Game mode (with/without PC mode), so you don't need to bother calibrating Game mode for SDR - just use an ISF mode in PC mode. For HDR, you must calibrate HDR game mode as well as a non-game HDR mode.
  • I found I had to use Warm1 as a basis for calibrating HDR Game mode, as opposed to Warm2. It is the hardest mode by far to calibrate.
  • Be aware how easy it is to accidentally execute an AV Reset and lose your calibrations. The combo is 3x Mute, then 'OK' or Red button. There is no confirmation dialog. Be careful with the Mute button.
  • LightSpace/ColourSpace might be a better purchase than Calman, but they are too expensive to justify buying both of, so I'll leave that for someone else to find out.
  • Lightning LUT seems to be the best option for calibrating SDR.
    • Fixed Grid does not cover any dark shades, so leaves you with nasty transitions into black - e.g. on my panel, very dark red is literally green using Fixed Grid (or without calibration), but Lightning LUT corrects it perfectly.
    • IR profile produced such a broken result for me that I am suspecting user error.
    • Lightning LUT leaves you with some noticeable colour error (and measurable using HCFR), but the result is more pleasing to the eye than the other options due to the gradient improvements.
    • An ideal option would be to composite the results of Lightning LUT and Fixed Grid, but that option does not exist (yet).
  • I can't find any evidence that turning off screen saving features (pixel shift and logo luminance adjust) is necessary. Would like to hope that LG programmed the internal pattern generator to defeat these features...
  • Spend some time with the TV uncalibrated - don't jump straight into calibration. I was almost going to live with the results of a naive Calman calibration and accept that my 4 figure TV had worse SDR picture quality than a 14 year old Plasma. The factory 1DLUT (and the factory 3DLUT in HDR) is absolute black magic at hiding OLED flaws, and you don't realise how bad they are or how much of a difference it makes until you go looking.
  • Certain aspects of the TV are not affected by 3DLUT or gamut settings - so far I have noticed this issue in: home screen, most app menus, the recommended content popups above the apps bar and the web browser.

The process I followed for calibration:

  • Setup low light mode etc as suggested in the Calman guides and YouTube videos. Anything not mentioned here should probably be followed, and is a one-time setting.
  • After starting Calman each time, go to Settings > Application Measurement Options > AutoCal targets > pick de_ITP in both dropdowns
  • For SDR I use 2.2 power curve gamma on both the TV and in Calman for day, and 2.4 on both for night. For HDR, the defaults on both.
  • As mentioned above, DO NOT calibrate the 1DLUT. LG standard one is miles better than anything else at hiding OLED flaws.
  • For SDR use the 3DLUT Autocal Lightning LUT. For HDR do not use any Autocal at all as it is hot garbage for HDR, just do a 2 point white balance.
  • If the SDR 3DLUT calibration has worked, you should be left with an editable gamma setting, an editable colour temperature setting (at Warm2), and a greyed-out/non-editable colour gamut setting at Wide. If the factory 1DLUT is disabled (very bad), all 3 of these settings will be greyed out.
  • Once calibrated with a 3DLUT (SDR) or as the only step (HDR), change to the Manual calibration workflow, then do a 2 point white balance calibration manually using the normal (not service) menu.
    • Repeat the 2 point many times with grey screen inbetween - the results vary A LOT. Seriously spend 30 minutes hammering away at this until you get values that still give low dE after not displaying a test pattern for a while. Do not just go with the first results that give a handful of low dE readings. OLEDs are not consistent.
    • For SDR, you may benefit from also calibrating 22 point mode, but only up to ~20 IRE at most. Mainly aiming to remove colour cast in dark shades, and possibly raise the darkest IRE if you cannot fully resolve black crush with the Brightness setting on your TV.
    • For HDR stick to the 2 point.
    • Ignore delta error solely from missing the gamma curve - LG knows best. You are only interested in fixing colour cast.
    • Don't adjust more than 2 out of 3 colours at any IRE.
    • Less is more - adjust as few IREs as possible.
    • For SDR keep some Photoshop radial gradients handy, and reset + start this stage again if they start looking too broken.
    • For HDR instead use: Mehanik HDR10 pattern 4.3 Linearization.
  • Be sure to verify calibration again, as doing the white balance AFTER 3DLUT is atypical, but because the majority of white balance adjustment is baked into the 3DLUT and we are just making minor tweaks afterwards, it should not have any great effect on colours. You can try doing a 2 point white balance, then 3DLUT, then a further white balance, but it is probably a waste of time.

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