Currently Being ModeratedSep 29, 2011 9:20 AM (in response to ILoveSax)
I reset the iMac numerous times and that did not help at all.
1. I unplugged both Cinema display, and iMac
2. I held the powder button for 1 minute.
3. Replugged everything
4. Pressed and held the power button until it "made the startup sound", then
5. Pressed and held "Option"+ "Command" +"R"+ "P" until it made the "startup sound" again.
Still, the brightness control would not come up until I pressed "command + F1"
Currently Being ModeratedOct 3, 2011 4:19 PM (in response to ILoveSax)
Mine just started missing yesterday after bringing my Macbook Pro in from the living room and hooking it back up to the 27" Cinema display.
No longer do I see a brightness control for the Cinema. Command + F1 just turns on mirroring and doesn't reveal the slider for me. Very frustrating as I used to adjust the brightness of the Cinema often.
Currently Being ModeratedApr 30, 2012 11:32 PM (in response to ILoveSax)
The exact same thing has happened to me.
I am running a 27" Thunderbolt display off of a Mid-2011 MacBook Air.
Suddenly, last week, my brightness control keys on my external keyboard stopped affecting the brightness of the Thunderbolt display. The brightness keys on the MacBook Air, though, still affect the brightness of the laptop's screen.
I went into the Displays preference pane, and sure enough, the brightness slider has disappeared.
Have you been able to resolve this? (zapping PRAM, etc doesn't work.)
I'm wondering if this is a glitch that came with 10.7.3...
Anyone have any ideas? I have no way, now, to control the brightness of my Thunderbolt display. It is EXTREMELY frustrating.