How to adjust the brightness of a second display connected to iMAC 2012 by Apple Mini DisplayPort to Dual-Link DVI Adapter?
How to adjust the brightness of a second display (Dell 3007WFPHC 2560x1600 dpi) connected to 27 inch iMAC 2012 through thunderbolt port by an Apple Mini Display Port to Dual-Link DVI Adapter?
iMac, OS X Mavericks (10.9.3), Mini Display Port