Force RGB mode in Mac OS X to fix the picture quality of an external monitor (Original)
Update: I have heard that 10.8.3 has solved this problem for some people, so I rolled back my changes and installed the update. No change on my monitor. Nevertheless, it’d be a good idea to update OS X before trying this, since it may fix the issues with your particular hardware.
I recently bought a MacBook Pro (with ‘Retina’ screen), but when I hooked it up to my Dell U2410 monitor via HDMI cable I was shocked by the poor picture quality. The contrast was all wrong and text was misshapen. No amount of calibration in the monitor or software would fix it.
Short answer: OS X thinks my monitor is a TV, and is using the YCbCr colour space rather than RGB. I had to override an EDID setting to force the RGB colour space, and it is now working correctly.
Long answer: I haven’t owned a Mac for a while and h