[GH-ISSUE #1459] Brightness control is not exact with the iMac 5k 2020 panel (LM270QQ1F1) #828

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opened 2026-05-05 06:45:16 -06:00 by gitea-mirror · 1 comment

gitea-mirror commented

2026-05-05 06:45:16 -06:00

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Originally created by @odedia on GitHub (Oct 26, 2023).
Original GitHub issue: https://github.com/MonitorControl/MonitorControl/issues/1459

Before opening the issue, have you...?

Searched for existing issues
Read through the Monitor-Troubleshooting Wiki
Updated MonitorControl to the latest version (if applicable)

Describe the issue

I am using a the iMac 5k 2020 Panel with a custom DisplayPort 1.4 board as shown here: https://youtu.be/0VXQu0fAc8s.

Overall it works amazing.

The only slight issue is that brightness control doesn't work 100% as expected - when playing with the sliders or the keyboard shortcuts, it will reach 100% brightness at 50% of the slider. From 50% to 100% it is basically at full brightness. From 50% to 0% it is working well.
Is there a way to override these settings? I know when my old Apple LED Cinema Display I needed to set DDC Max to 250 to get it working as expected. I tried it with this new setup but it doesn't do much.

Expected behavior

Brightness control works from 0% to 100%

Anything else?

No response

Environment Information (please complete the following information)

- macOS version: macOS Ventura 13.6
- Mac model: MacBook Pro M1 Max 16"
- MonitorControl version: 4.2.0
- Monitor(s): Apple LED Cinema Display, MacBook Pro built-in display, custom iMac 5k 2020 panel LM270QQ1F1
- Monitor Cable(s)/Connection(s): DisplayPort 1.4 connected via Thunderbolt 3 WD19 dock
- Apple Silicon/M1 (yes or no): Yes

Originally created by @odedia on GitHub (Oct 26, 2023). Original GitHub issue: https://github.com/MonitorControl/MonitorControl/issues/1459 ### Before opening the issue, have you...? - [X] Searched for existing issues - [X] Read through [the Monitor-Troubleshooting Wiki](https://github.com/MonitorControl/MonitorControl/wiki/Monitor-Troubleshooting) - [X] Updated MonitorControl to the latest version (if applicable) ### Describe the issue I am using a the iMac 5k 2020 Panel with a custom DisplayPort 1.4 board as shown here: https://youtu.be/0VXQu0fAc8s. Overall it works amazing. The only slight issue is that brightness control doesn't work 100% as expected - when playing with the sliders or the keyboard shortcuts, it will reach 100% brightness at 50% of the slider. From 50% to 100% it is basically at full brightness. From 50% to 0% it is working well. Is there a way to override these settings? I know when my old Apple LED Cinema Display I needed to set DDC Max to 250 to get it working as expected. I tried it with this new setup but it doesn't do much. ### Expected behavior Brightness control works from 0% to 100% ### Anything else? _No response_ ### Environment Information (please complete the following information) ```markdown - macOS version: macOS Ventura 13.6 - Mac model: MacBook Pro M1 Max 16" - MonitorControl version: 4.2.0 - Monitor(s): Apple LED Cinema Display, MacBook Pro built-in display, custom iMac 5k 2020 panel LM270QQ1F1 - Monitor Cable(s)/Connection(s): DisplayPort 1.4 connected via Thunderbolt 3 WD19 dock - Apple Silicon/M1 (yes or no): Yes ```

gitea-mirror closed this issue

2026-05-05 06:45:19 -06:00

gitea-mirror commented

2026-05-05 06:45:23 -06:00

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Owner

@waydabber commented on GitHub (Oct 27, 2023):

disable DDC and the scale will be uniform. By default the app uses software dimming from 0-50% and DDC from 50-100%. Seems like the board is not DDC compatible so hardware backlight control is not happening.

@waydabber commented on GitHub (Oct 27, 2023): disable DDC and the scale will be uniform. By default the app uses software dimming from 0-50% and DDC from 50-100%. Seems like the board is not DDC compatible so hardware backlight control is not happening.