Hello, Over the past four years I've been running OSX 10.8 (Mountain Lion) on a 2012 MacBook Pro Retina which is connected to 2 x DGM IPS-2701WPH LCD IPS Monitors via Display Port cables that are plugged directly into the MacBook Pro's Thunderbolt Ports. With this setup I've enjoyed fantastic high quality full resolution output (2560 x 1440) on the 2 monitors running alongside the MacBook Pro's Retina screen - until I updated to macOS Sierra. As soon as I upgraded from OSX 10.8 to macOS Sierra the 2 x DGM external monitors looked a bit blurry. Type now has jagged edges and images look a little out of focus and less sharp. Dragging a window featuring images and text from the Retina MacBook Pro screen and either of my DGM external monitors instantly shows up the poor quality that the external monitors are now providing. The macOS 'Preferences/Display' settings say the Mac is outputting to the 2 x DGM external monitors correctly at 2560 x 1440, but the quality is obviously worse than it was when 10.8 was installed. I've tried restarts, SMC reset, unplugging and replugging the Display Port cables etc. but the low quality remains exactly the same. It's frustrating as the monitors have worked beautifully with images very similar in quality to the Retina screen for the past 4 years. All helpful comments appreciated.