How could I use my iMac 27" Mid 2010 as an external monitor for my MacBook Pro Retina, 13-inch, Late 2012?
I have an HDMI to HDMI but nothing happens.
You use Target Display Mode via Thunderbolt cable.
Target Display Mode And Thunderbolt
Target Display Mode 2009 & 2010 iMacs
Target Display Mode 2011 & Later iMacs
iMac (Mid 2011)- Target Display Mode does not work with Mini DisplayPort cable
As your iMac doesn't have thunderbolt you need to use a Mini DisplayPort cable from the MBP's TB port.
hook them up and hit command+F2 your MBP desktop will appear on the iMac screen.
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