Both 'dual' controls show in OS for brightness, but they both only ever control one of the two monitors.

Basic Summary

When I plug in dual thunderbolt displays, everything appears okay until adjusting brightness > last connected monitor 'steals' both dual brightness controls. Only way to adjust brightness is to disconnect the other and set it on the remaining, and vice versa. Makes it tricky and painful to make brightness adjustments. (especially painful given the cost).

What I've done

Called Apple support they seemed totally lost, and wanted to push me to LG, did usual PRAM and SMC, deleted/adjusted basic colour profiles, then was asked to reinstall OS. All done. Problem remains.

Searches coming up totally blank. Tried installing LG's 'screen manager' software, no dice. Tried changing the ports used on the MBP.

Sidenote: the screens when brand new had a very different colour 'warmth', with one being very cold, and the other very warm. I've adjusted this with a lot a colour profile adjustments manually, but suspect this wasn't normal, and could be related. Also no ambient light sensor option (but this seems normal for other LG 5k users currently).


  • 2017 MacBook Pro, 15", 3.1 GHz, i7, 16 GB
  • macOS 10.13
  • Graphics: (2 listed?) 1. Radeon Pro 560 4 GB, 2. Intel HD Graphics 630 1536 MB
  • Monitor: 2x Thunderbolt LG UltraFine 5K Display (software version listed in LG screen manager is 3.04,1.13,5235,3.04,0.1e - not clear if this is the LG screen manager software version or the firmware version. it says 'the software is currently up to date').

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