Need Help with External Monitors

[gthorson]

I own a Late 2014 27" Retina 5K iMac with the AMD Radeon R9 M290X (2GB).

According to MacRumors, this iMac can drive one 4K display at 60Hz over Thunderbolt and one additional 2,560×1,440 display.

I currently have two additional 23" monitors (Dell U2312HM) running at 1920 x 1080 resolution. I'm unhappy with the text quality for websites/email/Word documents and want to upgrade my two monitors.

Should I opt for two Dell P2415Q 4K monitors or two Dell U2515H monitors (2560 x 1440)?

Will there be a problem with the refresh rate if I add two 4K monitors and scale them back to 2560 x 1440?

 

[andy9l]

Assuming you're correct with regards to compatibility, if you go for two 4K monitors, you'll have to run at least one of them at 2560x1440 (low resolution mode), which will look far worse than a native 2560x1440 monitor.

This is because your iMac cannot drive all the pixels required to use macOS's high DPI scaling. To use the high DPI scaling options in System Preferences, you need to be able to drive the native resolution of the display.

Getting macOS to scale the output on a 4K display to 'look like 2560x1440' is NOT the same as sending a 2560x1440 input signal to a 4K display.

As such, I'd recommend 2x U2515H 1440p monitors.

 

[gthorson]

Assuming you're correct with regards to compatibility, if you go for two 4K monitors, you'll have to run at least one of them at 2560x1440 (low resolution mode), which will look far worse than a native 2560x1440 monitor.

This is because your iMac cannot drive all the pixels required to use macOS's high DPI scaling. To use the high DPI scaling options in System Preferences, you need to be able to drive the native resolution of the display.

Getting macOS to scale the output on a 4K display to 'look like 2560x1440' is NOT the same as sending a 2560x1440 input signal to a 4K display.

As such, I'd recommend 2x U2515H 1440p monitors.

Thanks you so much, andy9l!