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I have an LG 42UB820V 4K IPS TV - 3840 x 2160 @ 60hz which I connected via an active mini display port to HDMI converter to use with my Mac Mini (HD4000) at 3840 x 2160 @ 30hz.

Everything works fine and dandy, using SwitchResX to make a custom resolution for 30hz.

The problem is I think OS X mistakenly takes the TV as a YCbCr device instead of RGB, or something along those lines. The fonts look awful, with some text having a kind of inverted halo around them!

Long story short, it actually showed the fonts perfectly at one time and it was beautiful, but after a restart it seems to have reverted to the 'awful' mode again.

How can I fix it now and forever?

  • Does it change when switching color profiles in system prefs? – Kevin Grabher Apr 6 '15 at 20:44
  • No, I mean the color do change a little bit but it's normal. – unom Apr 6 '15 at 21:56
  • If you turn off font smothing (i believe in general oder appearance) does it get better or worse? – Kevin Grabher Apr 6 '15 at 22:01
  • About the same, the sub pixel 'shadow detail' on each letter goes away, but still each character seems jagged as if antialiasing is doing something wrong. For example the letters 'l' and 'L' are nearly always supposed to be displayed perfectly, but here sometimes the upper part of the L is thiner in one word and thicker in another. – unom Apr 6 '15 at 22:06
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    @KevinGrabher Managed to zero in on the issue. It seems the LG TV has somekind of processing going on behind the scenes and it just activates even though it's turned off. If I go to the image settings and go into Cinema mode, or any other mode and the back to my custom settings, the effect is gone. – unom Apr 8 '15 at 11:23
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I have/had a similar problem with my MacBook Pro and now my newer MBPr with an Asus 27" monitor. I ended up finding a discussion about it and a script in a forum for Dell Monitors. The script took the monitors EDID information directly and created a display profile for it that overrode what OS X was trying to automatically configure.

Here is the script on github along with a link to the original topic. https://gist.github.com/ejdyksen/8302862

This worked for me to make my fonts readable again on my Asus VE27q.

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