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Brightness of external monitor

Hello! I am unable to adjust the brightness of my external monitor (iMac mid-2010) when I am using it as a secondary display to my MacBook Air (2020). When I press F1 and F2 it only changes the brightness of my MacBook Air, but not the iMac. I tried downloading the brightness slider app, but it does not solve the issue. Does anyone have a solution to this? Thank you!!

Posted on Nov 2, 2020 6:58 PM

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Question marked as Top-ranking reply

Posted on Nov 3, 2020 7:11 AM

To control the brightness of the iMac display while it's in target display mode, use Displays preferences on the other Mac, or the Brightness keys  on the keyboard of the other Mac.


-from this article about Target Display Mode:


Use your iMac as a display with target display mode - Apple Support


Since that article (and the feature) has now gone unsupported, I expect Apple will not fix it.


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Your only recourse may be to set the iMac brightness before you begin, then restart in Target Display Mode. If the Brightness is saved in Parameter RAM, it may be carried over to Target Display Mode.



8 replies
Question marked as Top-ranking reply

Nov 3, 2020 7:11 AM in response to karolina265

To control the brightness of the iMac display while it's in target display mode, use Displays preferences on the other Mac, or the Brightness keys  on the keyboard of the other Mac.


-from this article about Target Display Mode:


Use your iMac as a display with target display mode - Apple Support


Since that article (and the feature) has now gone unsupported, I expect Apple will not fix it.


--------

Your only recourse may be to set the iMac brightness before you begin, then restart in Target Display Mode. If the Brightness is saved in Parameter RAM, it may be carried over to Target Display Mode.



Nov 3, 2020 7:48 AM in response to Grant Bennet-Alder

Hello again,


Yes, I saw that article, but it still does not work. When I press the F1 and F2 keys on my keyboard it again only changes the brightness on my Macbook Air, and the brightness on my iMac remains the same.


And when I adjust the brightness of my iMac prior to using it as a secondary display, it automatically goes back up the moment I switch (by pressing command + F2).



Brightness of external monitor

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