When we buy a laptop or desktop from Apple, we are sure that we will be able to do everything, however, when we connect our desktop to a power source external video Like a TV or projector, we cannot easily and quickly darken the screen of the main equipment.
The same happens when we do AirPlay with our Apple TV. While we are with the AirPlay active, the screen of the desktop computer is also seeing the same.
For this, we bring you today a solution through a third-party app. It's about the app Shades. When we install the application, it is not installed in the applications folder, but is housed in the System Preferences panel. When you access it, we will see that there is a button with the word "start". When you click on it, the application searches for the connected screens and dims them as if you were wearing sunglasses. We can adjust the dimmer but we cannot completely turn off the brightness.
Well, as you can see, this is one of the options that we present to you to control this problem when connecting an external monitor to an iMac, for example. If you know of any other way to do it, do not hesitate to comment at the bottom of this post.
More information - [Video] OS X Mavericks connected to multiple monitors
Source - Shades