2 External Montiors forces Mirroring?

[Traverse]

I am working on a big project so I wanted to connect my 15" rMBP to my 1080p external monitor and an old 1600 x 900 monitor and use the built in display for 3 displays

The 1600 x900 is connected via DVI-D and the 1080p is connect via HDMI, but when I plug both in my system mirrors the same thing to all three displays and I can't find the option to change this.

Can't I use 2 external monitors for extreme screen real-estate?

 

[simsaladimbamba]

Does the following help?

System Preferences > Displays >> Arrangement >>> Mirror Displays (but know, that the display with the lowest resolution determines the maximum resolution used on both, thus one display will have a lower than native resolution, except when both displays have the same native resolution)

 

[Traverse]

I'm sorry, I was in the wrong display's settings to adjust the mirroring option.

 

[mmomega]

System Preferences -> Displays -> Arrangement

With multiple displays there will be a "Mirror Displays" box

If this box is checked, then the resolution will be the same across all monitors and they will all display the exact same thing.
So this means if you have a 1440p screen and a 1080p screen, the 1440p will drop to 1080p resolution since the 1080 can not increase to 1440p.

Also, if this box is not checked, I would try checking and then unchecking and then restarting the machine with the displays connected to see if this may solve your problem.

On my iMac, sometimes after 1 restart my screen will just randomly mirror each other, I restart a 2nd time and things go back to normal.
For me normal means no mirroring at all.