Marvin H.

Q: Trying to solve two problems when using iMac as second display for Macbook Pro

I have a new Macbook Pro and am using my late 2009 iMac as a second display. I'm using a Mini Displayport cable to connect the two computers together. When I hook up the cable the iMac automatically goes into extended display mode, when I close the Macbook screen the iMac mirrors the Macbook display. So far so good. I've got everything working the way I want except for two nagging problems.

 

1) I have not found a way to adjust the display brightness on the iMac after it is mirroring the Macbook display. The Macbook hot keys do not make any changes and the system preferences display page does not have a brightness slider. If I do a screen share to the iMac the system preferences display page has a brightness slider but moving it or using the keyboard hot keys does not change the brightness. When not connected together I can adjust the brightness of either screen. If I turn both screens to minimum brightness and then connect them together the iMac screen goes to full brightness. I've tried a number of suggestions I found on the internet but so far nothing has worked.

 

2) If while mirroring the screen I disconnect the battery charger from the Macbook the iMac screen goes dark after a few seconds. I've tried adjusting everything in the system preferences energy saver but so far I have not found a way to keep the iMac screen alive with the Macbook charger disconnected.

 

Thanks

iMac, OS X Yosemite (10.10.5), 27in, 8GB RAM. 2.66GHz Core i5

Posted on Aug 25, 2015 8:15 PM

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Q: Trying to solve two problems when using iMac as second display for Macbook Pro

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