In the old days when you purchased a monitor you had to decide between higher resolution and larger text. If your monitor’s native resolution was too high, you were plagued with either living with small text or running the screen at a lower resolution. People buying a 4K monitor today see the same issue, but there is now an easy way to get that running in Retina mode.
Apple’s solution to this issue was to introduce what they call “Retina displays” on Macs. That simply means a monitor where your effective number of pixels displayed is less than the actual number of pixels displayed. The screen on the iMac with 5K Retina Display screen will have four actual pixels – two vertical and two horizontal – for each effective pixel. By doing this at high resolutions, the result is text that is crystal clear and print-like without any individual pixels being apparent.
Enabling Retina Mode on your Third-Party 4K Monitor
Your Retina-capable Mac will default to using this Retina mode for its built-in monitor, but it will not do so for any external, third-party monitor. The good news is that a simple System Preferences tweak in Mavericks 10.9.3 and later will allow you to set Retina mode manually for your third-party, 4K monitor. Just confirm that your Mac will drive a 4K monitor before making your purchase.
Go into System Preferences > Displays and you should get a separate window appearing on each of your attached monitors. The “Default for display” option will likely be selected and, as mentioned, on your non-Apple 4K monitor that will result in very small images and text. Here is where you choose “Scaled,” after which you’ll have a series of five options ranging from “Larger Text” to “More Space.” Fear not: regardless of which option you choose here your Mac will still be sending information to your screen at full resolution, it will just be using those extra pixels to smooth out the elements it is displaying. Fonts will be smooth and clear and those jagged edges of your windows will be a thing of the past.
If you want to actually have your Mac send a lower-resolution image on your monitor, or if you simply want to choose an option different from one of the five that are presented, Option-click the word “Scaled” in this preference pane and you’ll get a much longer list. Check the “Show low resolution modes” box to see all your options. Anything with “(low resolution)” displayed will actually send that resolution to your screen. Everything else will send a full-resolution image to your screen in what we’ll call “Retina” mode.
Low Resolution Mode is Available on Built-In Displays, Too
Even if you don’t have a third-party 4K monitor you can still experiment with these options. The Displays preference pane acts the same way with your Mac’s built-in Retina display, too, except that “Default for display” automatically chooses the Retina mode.