Led Cinema Display brightness control not working after upgraded to macOS Monterey

In my case (27" Cinema Display) Lunar is what worked. I did not uninstall Monitor Control until I had verified Lunar was working. I was able to properly color calibrate after Lunar restored brightness controls. It was very straight forward fix in my case. To be clear I tried Monitor Control first with various suggestions and it did not work for me.

in my case, I can power off the Cinema Display using the button in the Lunar menu bar drop down menu, so I know that Lunar can 'see' the Cinema Display but Lunar doesn't change, let alone increase brightness at all.

I must admit to being quite confused by the many Lunar settings. Being under the impression that it should work straight away, I have not changed any of them but perhaps someone who know more about could suggest otherwise?

After installing MonitorControl, first thing I did was using the keyboard to adjust the brightness... the display immediately turned to 50% (oh no!!). Then I filled "DDC max" to 255, nothing happened. But after toggeling "Use hardware DDC control" the display turned to about 80% of brightness. Not good for me because I'm a photographer, highly reliant on the right brightness of the display. But after closing/reopening MonitorControl... whoosh! Brightness was on my side 100% ;) Also after restart and sleep.

After opening the app's preferences the brightness was back to 80% and the "DCC max" field was empty again, so I filled in 255 again and everything is fine now.

So MonitorControl seems a little buggy but I'm very thankful to the guys/girls who did it ..!!!

Thank you for your suggestions. In case of a conflict between Lunar and MonitorControl, I quit Lunar and made the adjustments to MonitorControl preferences that you describe but all to no avail. My Cinema Display remain resolutely stuck at 50% brightness and nothing will increase it.

It is both frustrating and tantalising, in that the onscreen Brightness display (when using the keyboard control) continues to rise above the 50% mark even without having any effect on the actual screen brightness. Sometimes a little lock symbol appears alongside but I have no idea how to unlock it.

To me this looks like a conflict between your apps and the system that doesn't know where to get the display info.

My suggestion would be to uninstall both apps and start all over again. As they don't come with an uninstaller you have to use AppCleaner to also remove all their system files.

Restart and just install MonitorControl as I have seen the best results with this app in my searches.

Note: In the past AppCleaner caused some problems with my F-Secure installation after uninstalling another app.

There's a solution for that here:

https://community.f-secure.com/safe-en/kb/articles/6282-f-secure-product-shows-error-notification-security-cloud-malfunction-on-a-mac-computer

Mac Mini M1, Led Cinema Display, Mini Displayport to USB-C

Thanks again. I think you may be right. I don't have AppCleaner but I do have Cleaner One Pro, which does the same thing. I'll run it and then reinstall MonitorControl, as you suggest.

I don't know what F-Secure is and don't anything installed with a similar name, so hopefully, will not have any issue in that regard. Will report back later.

Nope, alas, no change at all.

Having done all that, my Cinema HD is still stuck at 50%.

From reading some of the other posts on this page, it would appear that a) this problem is mostly particular to M1 Macs running the latest OS, and b) some have had some success connecting their Cinema HD to an older Mac running an older OS. It seems that when doing so, the brightness of the Cinema HD can be taken to the maximum and that sets the brightness when reconnecting to the newer M1 Mac.

Sounds a little far fetched but at this point, I'm running out of options!

BRB

That doesn't sound far fetched to me. My Led Cinema Display was connected to an old Intel Mac Pro and the brightness was set to 100% as I disconnected it. When I connected the display to the Mac Mini M1 the brightness was still at 100%, but had no slider nor keyboard control.

Only after installing MonitorControl it got stuck at 50% as the max. But as I said after toggeling "Use hardware DDC control" it came back at 100%.

Btw F-Secure is a virus and spyware scanner.

Indeed, it did work, in part.

I connected the Cinema HD to my MacBookPro and the brightness was immediately improved, to around 70%-80%. Unfortunately, the connection seemed to affect the trackpad (mouse also) and I could not control the cursor to adjust Display brightness in Preferences.

On reconnecting the Cinema HD to the Mac Studio, the brightness was maintained at the same level, which is a big improvement. MonitorControl, with settings as previously suggested, had no further effect on brightness, however.

On disconnecting the Cinema HD from the MacBook Pro, trackpad (and mouse) functionality returned to normal.

Do you have an old wired mouse somewhere? They tend to always work. You can connect the USB-A plug of the display to your Macbook, and the mouse directly to the display.

Also you can try to set your keyboard to move the cursor in Accessibility preferences. Or quickly hit the Option(cmd) key five times, that should activate Mouse Keys. Then you can use the keys 7 8 9 U O J K L to move the cursor. On an extended keyboard you use the number keypad on the right.

Or you can bring your display to a friend with an Intel Mac and set it to 100% there ;)

Yes, thanks. I did connect a mouse via USB - USB C converter but the MacBook Pro struggled with that too. The 5x Option key trick is new to me though. I will keep it in mind when I next attempt to get to 100% brightness.

Only slight snag holding me back from doing it right away is that each time I disconnect and reconnect the Cinema HD display to the Mac Studio, the Display Preferences go a little berserk, the CinemaHD becomes the primary monitor instead of the extension, their relative positions get reversed and if the iPad is connected too, it has a minor nervous breakdown! Alright, it's not the end of the world but it is quite annoying and time consuming to get everything back in order.

Again, ran through the process of setting the brightness on the Cinema HD via the MacBookPro. No connection issues this time but there was no extra brightness to be got, nor any way of adjusting it. Tried again via an iMac running BigSur but again, no control or adjustment in brightness.

Reconnected the Cinema HD to the MacStudio. It flickered to life briefly then went black and though still visible in Displays Preferences and MonitorControl, would not respond to either. Restarted and rebooted but still black.

Not sure what to try next?

Of course, it could be that the Cinema HD has reached the end of its natural life. Can it be repaired? I have two of these former beauties, now both defunct alas. It would be lovely to get at least one of them back to useful life.

Update...

Shut down, checked all the connections and restarted. Bingo! Cinema HD is back up and a little brighter than before, around 85%-90% brightness, I'm guessing.

I'm guessing because nothing controls it anymore, not the Display Preferences, nor MonitorControl where it no longer appears at all.

I'm stumped!

But as a general conclusion, connecting to an older machine with an older OS does seem to enable better brightness, albeit with no actual control. For me, anyway.

Thanks, nguyendk, that's actually very helpful. I did try connecting the Cinema HD to my MacBook Pro but hadn't installed Monitor Control on the laptop and only managed to get the monitor up to about 85% when reconnected to the Mac Studio.

Incidentally, the flickering and black screen I mentioned in an earlier post was caused by overheating, I've since discovered. A problem that was exacerbated by the positioning of the monitor in direct sunlight. It has never been a problem before but the extreme high temperatures we've been experiencing this year must have put it over the edge. Switching off the power and allowing the monitor to cool off seems to do the trick.

Your display settings probably got bungled at some point. Try moving all files in the folder ~/Library/Preferences/ByHost that starts with com.apple.windowserver.displays to a different location for backup and restart your computer. If it doesn't work, try another port on the machine. If it still doesn't work try one of the other suggestions like MonitorControl or Lunar.