Reports of the issue:
This blog post has excellent advice on solving the clarity issues when you run a Retina-level external monitor - and you run it at lower-than-native resolutions, which is 90% of the time. Hardly anyone runs their Hi-DPI monitors in Native res. The type is too small. When you lower MacOS’s resolution down to anything below Native, now you’ve got blurred text. This is due to fractional-math problems because the external monitor is 163 PPI and your MacBook Pro is 221.
The most important spec to pay attention to on these monitors is Pixels Per Inch (PPI).
Buy a monitor with a PPI that matches your Retina MacBook or older MacBooks, but nothing in between. (The older ones were about half, at 128 PPI.)
- MacBook Pro: 221 PPI
- Old MacBooks and Airs: 128 PPI
Get a monitor that’s either 221 or 128 PPI (or as close as you can reasonably) - give or take 10 PPI.
MacOS is has two sets of UI widgets. It sends the Hi-Res ones to 4K+ displays, and the low-Res ones to anything under 4K. If you’re running one of these PPI’s in between 128 and 221, the OS is going to have to scale things in odd ways.
Important: MacOS only sends Retina assets to 4K or greater monitors. The PPI doesn’t matter. I’ve seen some confusion about this online. Folks buying a Hi-PPI monitor, but one that’s only 3K, and they’re wondering why it doesn’t have Retina assets. MacOS can only “see” the resolution (Pixel count) of the display. It can’t see its “PPI” specs.
Some PPI specs for comparison.
- 2012 MacBook Air - 128 PPI
- 2020 MBP - 226 PPI
- Apple’s $5,000 Pro Display - 218 PPI
These will be sent non-Retina assets by MacOS. Note the PPI roughly matches old MacBooks and MBAs.
- 1080p - 91 PPI in a 24” mon 👍 - Good for Mac
- 1080p - 81 PPI in a 27” mon 👍 - Good for Mac
- 2560x1440 (Quad HD) - 108 PPI in a 27” mon 👍 - Good for Mac
- HP 27er display - 82 PPI 👍 - Good for Mac
- 3,840 x 2,160 - 163 PPI in a 27” 👎 - Bad for Mac - PPI is at this dangerous midpoint between MacBooks and MBP.
- 3,840 x 2,160 - 138 PPI in a 32” 👍 - Good for Mac - PPI roughly matches non-Retina Apple screens (128).
For office and creative work, go with IPS. For gaming, go with TN:
- TN - Most affordable. Low image quality but hi-refresh.
- IPS - Best overall quality. Higher input lag. For Pros doing graphics work.
- VA - Better color and contrast than TN. Not as much as IPS.
- OLED - Absolutely killer. Baller expensive.
Adaptive Sync is a variable-refresh technology. GSync is a brand name for one.