Can 12-inch MacBook do 2k HiDPI on external 4k monitor?

orbitalpunk

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Original poster
Aug 14, 2006
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I have 2015 MacBook and I keep reading that it supports 4k external monitors. But when I connect mine, the 4k resolution option says (low resolution) next to it and the image is fuzzy. But 1080p says HiDPI and its sharp as a tack. So why is 4k or 2k resolutions labeled (low resolution) when Apple support pages say it supports 4k? Am I missing a step?
 

jerwin

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Jun 13, 2015
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The way I see it, you have three choices for resolution.

3840x2160 (looks small-- this is the native resolution of the display)
1920x1080 hiDPI (looks smooth and sharp, like a laser printer)
1920x1080 lowDPI (looks sharp, but slightly blocky)

Anything else will have undesirable antialiasing effects.

What you have selected in this graphic


should work just fine. The graphics are just as smooth and sharp as on my 5k iMac, so just enjoy it.
 

orbitalpunk

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Aug 14, 2006
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1080p doesn't give me enough screen real estate. cant even put two document side by side. the graphic you asked about was 1920x1080, thats what you see selected.
 

jerwin

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Jun 13, 2015
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Could you post a screenshot of the entire screen?

(command shift3)

This is from my 1080p secondary display. lodpi, of course, but the proportions should be the same as on your 4k display.

Screen Shot 27(2).png


Now, if the control panel takes up vastly more space, there's a problem.
 

bill-p

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Jul 23, 2011
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It's just the display not supporting additional timings beyond 1080p HiDPI. I think you can add more timings with SwitchResX (I have tried it with 2016 MacBook but not with 2015), but then I would not recommend going higher than 1080P HiDPI on the 2015 MacBook due to performance issues. The 2016 model is better, and the 2017 model is pretty much perfect when it comes to display scaling.

Here's 3360 x 1890 HiDPI on a display that actually supports the timing for the resolution.

 

EugW

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Jun 18, 2017
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It's just the display not supporting additional timings beyond 1080p HiDPI. I think you can add more timings with SwitchResX (I have tried it with 2016 MacBook but not with 2015), but then I would not recommend going higher than 1080P HiDPI on the 2015 MacBook due to performance issues. The 2016 model is better, and the 2017 model is pretty much perfect when it comes to display scaling.

Here's 3360 x 1890 HiDPI on a display that actually supports the timing for the resolution.

What do you mean by performance issues on the 2015? Lag and stutter?

As for the 2017 being “pretty much perfect”, what do you mean? You show a picture with 3360x1890 but why? What’s the point of running that?

Sorry for all the questions, but I have the 2017 so I’m curious.
 

bill-p

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Jul 23, 2011
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The 2015 model runs 4K at sub par performance in my experience. It is entirely possible I was pushing the machine too far, and I was spoiled also by the performance of the 2016 rMBP, but it was not workable for me at least.

Then I upgraded to a 2016 model and it was much better than the 2015 model. Workable, at least, when you disable transparency effects.

And then the 2017 that I just upgraded to has improved a bit more so now 4K performance is pretty much on par with the 2016 rMBP. Of course still with transparency disabled.

I'm showing 3360x1890 because:

1. OP asked if 12" MacBook could scale beyond 1080P for HiDPI. I wanted to provide proof that it actually could. 3360x1890 is in HiDPI mode there. The actual internal resolution is about 6720x3780 with everything doubled up. Then all of that is scaled down to 3840x2160.

2. What's the point of running 3360x1890? Well, it's between 2560x1440 and 3840x2160. If you find 3840x2160 too small for comfort, and 2560x1440 is too big, then you can use 3360x1890 instead. This makes sense for some bigger TVs (like 50" 4K) when you add it as an extra resolution with SwitchResX.
 
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EugW

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Jun 18, 2017
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The 2015 model runs 4K at sub par performance in my experience. It is entirely possible I was pushing the machine too far, and I was spoiled also by the performance of the 2016 rMBP, but it was not workable for me at least.

Then I upgraded to a 2016 model and it was much better than the 2015 model. Workable, at least, when you disable transparency effects.

And then the 2017 that I just upgraded to has improved a bit more so now 4K performance is pretty much on par with the 2016 rMBP. Of course still with transparency disabled.

I'm showing 3360x1890 because:

1. OP asked if 12" MacBook could scale beyond 1080P for HiDPI. I wanted to provide proof that it actually could. 3360x1890 is in HiDPI mode there. The actual internal resolution is about 6720x3780 with everything doubled up. Then all of that is scaled down to 3840x2160.

2. What's the point of running 3360x1890? Well, it's between 2560x1440 and 3840x2160. If you find 3840x2160 too small for comfort, and 2560x1440 is too big, then you can use 3360x1890 instead. This makes sense for some bigger TVs (like 50" 4K) when you add it as an extra resolution with SwitchResX.
Thanks. BTW, what dongle or cable are you using for your external display on the 2017? It's been a crap shoot for dongle compatibility, since the 2017 has changed something vs the 2015/2016.

For HDMI the first dongle I bought, which is compatible with the 2016, does not work with my 2017. Plugable has since confirmed it doesn't work with their 2017 iMac either. Their DisplayPort cable works, but obviously that isn't HDMI. I'd consider the Apple AV adapter with HDMI, but unfortunately it costs about 3X as much as a plain 3rd party dongle, and it too is reported to be flaky, even on the older model MacBooks and MacBook Pros.

In the meantime, for DisplayPort support, I have ordered a Monoprice USBC DisplayPort dongle and an eBay noname USBC Mini-DisplayPort dongle, but again it's a crapshoot from what I gather. Dongles that are compatible with the 2015/2016 are not necessarily compatible with the 2017.
 

bill-p

macrumors 68000
Jul 23, 2011
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My display has native USB-C support so I just plug the MacBook in with USB-C. No need for dongle.

But yeah, I have also found that not too many dongles support 4K @ 60Hz. The ones that do don't pass along power, and there was no USB-C splitter so I had to solder my own splitter for separate power and data. Too much hassle that way, and that ultimately pushed me to get a USB-C display either way. I liked like the convenience so much that I got the same display for work as well, so now I have the same experience both at work and at home.
 

jeff-4

macrumors newbie
Mar 30, 2016
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My display has native USB-C support so I just plug the MacBook in with USB-C. No need for dongle.

But yeah, I have also found that not too many dongles support 4K @ 60Hz. The ones that do don't pass along power, and there was no USB-C splitter so I had to solder my own splitter for separate power and data. Too much hassle that way, and that ultimately pushed me to get a USB-C display either way. I liked like the convenience so much that I got the same display for work as well, so now I have the same experience both at work and at home.
Could I ask you what display model you have? After unsuccessfully trying to use my Thunderbolt monitor with my new MacBook 12" 2017, I am looking for a suitable, single-cable USB-C display (with ethernet and USB-A ports built in). Any recommendations?