I have a mid-2013 MacBook Air powering two Thunderbolt Displays. I have my MBA plugged into the first display, and then I'm daisy-chaining the second, exactly as Apple intends. Both monitors turn on, are responsive, etc., but there is no brightness control for the secondary display. I physically swapped positions of these displays to confirm that Display #2 wasn't defective, and it is not. The primary display goes from max brightness to min brightness without any qualms, but the secondary one will not adjust at all, and instead remains very dim throughout use. I have tried Control + F1/F2 (using Mavericks, OS X 10.9) and it does absolutely nothing on the secondary display. You can see that even in System Preferences, there's no Brightness Slider for Display #2, regardless of where I set the Dock. Image is here: https://www.evernote.com/shard/s31/...0b12ff474a1c/skitch.png?resizeSmall&width=832 Any help would be greatly appreciated!