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Setting up a 4K monitor on a Mac

This article will cover some of the basics of setting up a 4K monitor on a Mac, and also give you useful information you are thinking of buying one. The OS version I used was 10.10.2 and the Mac was a late 2013 MacBook Pro 15 Inch Retina. The options on different OS versions and different Macs will vary. Updates may improve 4K support as well. The monitor used was an EIZO ColorEdge CG318. At the time of writing using a 4K screen on a Mac isn’t plain sailing. This is partly down to the graphics cards in Macs, partly OS and driver issues and partly down to the monitor manufacturers and Apple needing to work together to get things sorted.

Apple have a very useful webpage that covers support for 4K monitors: http://support.apple.com/en-gb/HT202856

It lists the Macs and OS versions that support 4K screens, including supported resolutions, connections and monitors. However, it doesn’t tell the whole story because it is possible to get a little more out of your Mac and improve on the default options. Also you can use more monitors than the ones the page lists.

4K Monitors, such as the EIZO ColorEdge CG318, have more than four times the pixels of HD.

4K Monitors, such as the EIZO ColorEdge CG318, have more than four times the pixels of HD.

Connecting your monitor

The first choice you get is what cable to use to connect the monitor. You can use HDMI or you can use Thunderbolt (the connector is the same as mini Display Port and Thunderbolt incorporates the Display Port 1.2 standard). Whilst both connections support the same resolutions the big limitation is that HDMI can only work at 24 hertz or 30 hertz refresh rates on the current crop of Macs. This makes using a Thunderbolt port the better option as you may be able to use 60 hertz instead. Slower refresh rates will make your Mac feel sluggish, the mouse movement won’t be as quick as you are used to and games or video won’t be as good.

The refresh rate problem is caused by the sheer amount of data that displaying 4K involves. Displaying full 4K (4096 x 2160) at 60Hz requires 16Gbps of bandwidth. HDMI 1.4a has a maximum bandwidth of 10.2 Gbps whereas Display Port 1.2 can handle up to 21.6Gbps. HDMI 2.0 will up the bandwidth possible to 18Gbps, but for now Display Port is the best option.

Display Port also supports Multi-Stream Transport via two cable connections. MST basically splits the monitor in half and each connection drives half the screen. This can speed up the refresh rates available but does have it’s own downsides as the Mac will treat each half of the display as a separate monitor. You will probably find that getting the ideal connection for your own purposes takes a little trial and error, especially if your monitor isn’t on Apple’s supported list.

There are two flavours of 4K screens. True 4K monitors have a resolution of 4096 by 2160. UHD monitors are 3840 by 2160. The screen I was using was an early release EIZO ColorEdge CG318 that is true 4K. When connected to my Mac it defaulted to 3840 by 2130 and had black space either side of the image. Configuring the screen for MST and using two connections got me the full resolution but I found the dual screen set up a little inelegant.

The Display preference pane didn’t show the option of 4096 x 2130, it just showed the default scaling options (more about those in a moment) but if I held the Alt key down when I clicked on the Scaling radio button I did get a more comprehensive list of resolutions, and got more information as to which refresh rate was being used for each setting. I also found some software called SwitchResX that also displayed many more options than the OS was giving me and enabled me to select the full native resolution.

Resolution Scaling

Most computer operating systems and applications define the size of text as being a certain number of pixels and assume a screen resolution of 96ppi. A standard HD resolution (1920 x 1080) monitor is does have a screen resolution of about 96ppi. A 27 inch monitor of 2560 x 1440 increases the resolution to 109ppi but a UHD 31 inch screen has a resolution of 140ppi. If you increase the resolution of the monitor the display size of text and other elements will get smaller. Going from a typical 24 inch to a typical 27 inch screen results in smaller type that may cause some users a problem but most will find the reduction acceptable. However, jump up to 4K or UHD resolution and the text gets incredibly small and I challenge anyone to find it useable for any length of time.

Realising this both Microsoft and Apple have built-in type scaling features that changed the apparent resolution of the monitor so that text becomes larger and more readable. Apple started doing this with their Retina screens. In the Mac OS  Display preference pane you can select a range of options that can either increase the size of text or let you have more desktop room to display your applications.

The Display preference pane allows you to scale the resolution of the monitor to improve legibility of text.

The Display preference pane allows you to scale the resolution of the monitor to improve legibility of text.

The Mac still sends all the data to the monitor in the full native resolution of the monitor but it processes it beforehand in the scaled resolution so that each pixel is displayed not by one pixel on the monitor but by several depending on the amount of scaling. The downside with scaling is that you may have bought a 4K/UHD display so that you have loads of room to display lots of windows/applications but in order to have readable text you end up with no more room than you’d have on a lower resolution screen. However, you do still get the stunningly crisp look of a high ppi screen and there is little or no loss of quality, although I did feel that some scaling settings were sharper on text than others. Also whilst most applications supported the resolution scaling one or two didn’t and hence looked quite low res.

Holding the Alt key down when selecting the Scaled option gives you a wider range of resolutions to choose from.

Holding the Alt key down when selecting the Scaled option gives you a wider range of resolutions to choose from.

On my Mac with the CG318 some of the scaling settings only worked at 24Hz, so I ended up with slightly larger text than I wanted so that I could stick to 60Hz. And unfortunately all the scaling options put the screen back into 3840 and not 4096 resolution. I’m sure that over time these kind of teething issues will get addressed as 4K screens become more common and support for them becomes more widespread. In the end the best set up for me was to use my MacBook screen for email etc, and even for all Finder operations like opening files etc and just use the CG318 for Photoshop, in its full native resolution. Photoshop itself has a interface text scaling option that meant I could still read the menus without eyestrain. Used in this way I got the full benefit of 4K with minimum downside, and I must say images looked truly stunning. It was more like looking at a good inkjet print than a monitor. You really couldn’t see the pixels at all, the image was superbly smooth and razor sharp.

 

Editing images with Photoshop in 4K on the CG318 was a joy. You get loads of space and pin sharp display.

Editing images with Photoshop in 4K on the CG318 was a joy. You get loads of space and pin sharp display.

Conclusion

All of the above is based on experience with one screen on one Mac, but it does prove the point that if you are going to be an early adopter of 4K or UHD monitors and you use a Mac you really do need to do your homework to ensure that you will be able to use your monitor on your Mac with a resolution and a refresh rate that you are happy with. 4K has obvious benefits but some downsides as well.

I’ll post a full review of the the EIZO ColorEdge CG318 and information on using a 4K/UHD monitor with Windows next week. Search our blog for 4K for further articles.

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