I have a iMac 27'' and a LED Cinema Display 27'' connected to it. And I've noticed that to be able to control brightness I need to open the Display.prefPanel and modify the brightness of the displays individualy.

Is there a way to do this simultaneously? Maybe with a third party app? If not, is there a way to assign a keyboard shortcut to the second display brightness?

  • How do you control Cinema Display brightness? My Display.prefPanel only have main screen brightness control.
    – Tinyfool
    Dec 10, 2011 at 9:08
  • Try <kbd>Control ⌃</kbd> and <kbd>F1</kbd> or <kbd>F2</kbd>. That should work.
    – daviesgeek
    May 14, 2012 at 17:35

4 Answers 4


I just started using Dimmer Than Dim, a free app in the App Store. I only have one display (iMac), however.


F.lux is worth a look, it changes the colour temperature and brightness of your monitor(s) based on the time of day.

  • 1
    Sadly F.lux is totally automatic and it really doesn't even change the display brightness. Jun 24, 2011 at 10:50

Shades can do this.

(I am pretty sure it can, I only have one monitor attached at the moment, so I can't verify.)

  • 1
    In my testing, Shades can control both individually but not simultaneously Sep 23, 2011 at 3:21

Lunar has Sync Mode which automatically detects changes in brightness on your iMac screen (even those made by the light sensor) and syncs them automatically to the LED Cinema display.

It doesn't use a software overlay. In fact, Apple vendored displays get special treatment as Lunar uses an implementation hidden inside macOS Display Services to control them natively.

Note that you have to connect the USB port of the LED Cinema to the iMac to enable the DisplayServices method of changing brightness to work.

Disclaimer: I'm the developer of Lunar

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