Brightness settings on iMac with a second display

Posted By on December 29, 2015

How do you control the brightness iMacDualDisplayBrightnesson Thunderbolt connected secondary monitor without any physical controls? This took me a few minutes to figure out … so its worth archiving as a tidbit.

When your display desktop is at a premium, or you are running virtual operating systems, having a second monitor is a real plus. I added a secondhand 27″ Mac Thunderbolt display to my iMac and love the extended desktop especially for a Parallels Windows 10 virtual machine; it now sits on it’s own large monitor. The small single Thunderbolt connection and matching resolution made this a no-brainer decision … but there was a glitch: I could not control the second monitor’s brightness setting?

There is a simple solution: Plug in the pigtailed USB wire from the Thunderbolt display (as well as the Thunderbolt wire) and then you can use ctrl-F1 and ctrl-F2 to dim and brighten the second monitor just as F1 and F2 controls the primary monitor.


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  1. lacking in consistency, constancy, or visible order, disconnected; fitful: desultory conversation.
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