displaymacos
I have recently purchased a Dell S2340l monitor to extend my MBPr late 2013 screen. So far I can say it's a great monitor, colors are great, but still in the test phase…
Whatsoever, I really love that the MBP auto-adjusts the screen brightness depending on the light in the room. Therefore, my question: is there any possibility that this feature can be extend to the secondary monitor as well?
System Preferences → Displays → Automatically adjust brightness
You can use Shady.
The way it works is that it...
...pull(s) a virtual shade over your screen ... dimming the display to a more comfortable level.
Shady will save your shade level and restore it next time you launch the app.
As it's just a virtual (but effective) dimming method, I doubt that this saves much energy, but I cannot confirm this as LED displays should consume less power if displaying darker colors.
Best Answer
I don't know about auto adjustment but the way around is you can creat a sort cut or using this app you can change it if there no hard button or program available for you monitor. Use this app. You can adjust brightness and also set shortcut for it
https://itunes.apple.com/gb/app/brightness-slider/id456624497?mt=12
Enjoy!