Update: 2020/12/01 for macOS Big Sur, please follow instructions here.
If you have a MacBook, iMac, or Mac mini and use a HDMI cable to connect to a Dell monitor, you may notice that the image seemed over-processed as if it was over-sharpened – I noticed this when I connected my MacBook Pro to my Dell U2913WM.
I found a setting in the monitor to turn the sharpness down from the default 50 to 0. It improved the image quality some, but when I switched back to my Mac mini (which was connected via DisplayPort), the quality was still better.
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It turns out that this is caused by the Mac sending video signals as YPbPr (component) instead of RGB. This can be seen in the Color Settings menu.
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Why does this happen? When a HDMI display is connected, the display’s capabilities are negotiated using what is known as an EDID. For some reason, Apple/Mac decided to default to YPbPr, and there’s no way for us to select/force RGB.
I found this blog, which also took a reference from another blog comment. TL;DR, download a small Ruby script and run it. The details are in those blogs, but I’m just writing it here for my own future reference.
Steps:
- Run the Ruby script. It will generate a folder with a file, e.g.
DisplayVendorID-10ac/DisplayProductID-4080
- Reboot your Mac in recovery mode (hold down Command+R)
- Copy the file to
/Volumes/Macintosh\ HD/System/Library/Displays/Contents/Resources/Overrides
- If the folder exists, copy the file into the folder.
- If the folder doesn’t exist, copy the entire folder.
- If the file already exists, make a backup before overwriting it.
- Reboot, and reconnect your display.
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The difference is immediately noticeable. (I also had to restore my sharpness back to default: 50.)
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