I have a late 2012 27" iMac as my primary monitor also connected to a late 2009 27" iMac as a secondary monitor via a mini-display port to mini-display port cable. I also have a Dell 24" monitor connected to the late 2012 27" iMac as a third monitor.
I can change the brightness on the Dell monitor manually with the Dell hard buttons but I cannot change the brightness on the late 2009 iMac using the keyboard attached to the late 2012 iMac
Is there anyway to change the brightness on the iMac which is serving as a secondary display?
- I don't want to use the software Shades as it’s a memory hog and leaks memory
- I'm using a wired Mac keyboard connected via usb to the late 2012 iMac
- control + F1 or control + F2 does not work.