Recently I wrote about plugging a Samsung U28D590D “4K” display into my late-model 15" MacBook Pro. Decent performance, easy setup. It was reporting 30fps, which is OK for programming, but Sheldon McGee a.k.a. @tooshel said that I’d get 60fps via DisplayPort, and pointed me at video evidence. So I tried, and here’s the data.

This is OS X 10.9.3 on a “MacBookPro11,3” i.e. late-2013 15" model. There are three possible configurations: Standalone laptop, Laptop/outboard via HDMI, Laptop/outboard via DisplayPort. For the latter to work, I had to buy a DP-to-mini-DP adapter; the Mac then reported the display as running at 60 Hz.

For the laptop screen, I investigated two resolution settings: “Best for display”, and the Native resolution of 1920x1200. For the outboard Sammy, I tested the “Best for Display” (which is I think 1920x1080), the second-highest-resolution, 3008x1692, which is what I actually use, and the Native resolution, 3480x2160.

I used two test videos; the 24fps-vs-60fps test by Marc Tönsing featured in Paul Bakaus’ The Illusion of Motion, and the first-half highlights from the Netherlands’s 2014 World Cup first-round thrashing of Spain, which contains van Persie’s incredible header. I used the CBC version, which is higher-rez than the one at FIFA.com, but you probably can’t see if you’re not in Canada. I tested the Tönsing video in both embedded and full-screen mode, the football highlights full-screen only.

Standalone Laptop · The Tönsing video 60fps ball was equally smooth at Best and Native display settings, which is what I’d expect. I’d thought earlier that plugging in the HDMI made the laptop display slow down, but couldn’t reproduce that finding.

Tönsing video on outboard screen · Via DisplayPort, at both Best and Native resolutions, there was no shimmy in the 60fps ball. But at 3008x1692, the 60fps ball shimmied just like the 24fps one.

Via HDMI, there was shimmy on the 60fps ball at all three resolutions, but the shimmy looked different in ways that are hard to describe. I noticed that in Native mode, I could only see the shimmy full-screen, not when leaving the video embedded.

Football highlights on outboard screen · Via DisplayPort, the highlights looked great at Best resolution, maybe a little worse at 3008x1692 (but I might have been fooling myself), and distinctly jittery (?!?!) at Native resolution.

Via HDMI, the picture was OK in Best and Native modes — maybe not quite as good as DisplayPort, can’t be sure, but perfectly good enough to enjoy watching. I’m pretty sure there was more jitter in 3008x1692, but once again I might have been fooling myself.

Conclusions · Draw your own, dammit. The fact that HDMI works just fine for displaying video of a football match shouldn’t be surprising, it was designed for TV after all. The fact that the DisplayPort showed jitter at native resolution was a little disturbing. Since I use this for programming, and since when I’m watching football I leave that on the laptop screen off to the side, I guess I’ll keep connecting by HDMI for now.

Note that the Sammy isn’t on the list of approved displays for 10.9.3; I got it because people reported that it worked and it was cheap and looked nice.

I’d be interested in the results of this test, run on a real Apple-approved Thunderbolt display.



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From: Paztrick (Jun 28 2014, at 19:14)

Quick correction 1920x1200 is not the native resolution of the MacBook Pro's display - that's 2880x1800. None of the resolution settings in the Displays System Preferences change this - the "looks like 1920x1200" mode simply renders everything at 3840x2400 and scales it down to 2880x1800 before sending it to the display itself.

You can, of course, set it to 2880x1800 with the help of third party tools, but things end up a tad crazy small then.

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From: opwe (Jun 29 2014, at 10:32)

"Native resolution" probably means "Laptop's built-in screen's native resolution", which means it's likely non-optimal for the external display, and that's where the jitter comes from.

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author · Dad · software · colophon · rights
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June 27, 2014
· Technology (87 fragments)
· · OS X

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