4K monitor with mid-2012 MBA Core i7

Discussion in 'MacBook Air' started by roninpawnee, Jun 9, 2015.

  1. roninpawnee macrumors newbie

    Jun 9, 2015
    I would like to buy the Asus PB287Q 4K monitor for work (coding , writing papers etc) and use it at 1/2 the resolution, i.e., 1920 X 1080 (my eyes are not great for a 30 year old.. can't do native 4K).

    I plan to upgrade to a 2015 MBA in 3 - 4 months from now, which I hear can run this monitor at 60 Hz and 1920 x 1080.

    However, I currently have a mid-2012 MBA Core i7 running Yosemite. Can I use this MBA to power a 4K display for a few months? Can I run it at 1920 x 1080 and 60 HZ?

  2. motrek macrumors 68020

    Sep 14, 2012
    Yes, the MBA can definitely put out a 1920x1080 signal which is what you need. The monitor then scales that up to 4K as necessary, so no worries about that. You could do that resolution with an HDMI cable even, no problem.

    I recall some "hacks" to get older MBAs to drive 4K monitors at 30Hz, not sure if that would work on a 2012 model or if it requires something newer. Some people think 30Hz is fine, others think it's too "jumpy". Wouldn't hurt to try. You will need a DisplayPort connection to do this resolution though, FYI.

    You can use a program called SwitchResX to enable high-dpi modes on your MBA. This will trigger Apple's "retina" software so you can display 1920x1080 worth of screen real estate at 4K, which makes everything very sharp obviously. I don't know what the performance penalty is for this, but couldn't hurt to try.
  3. roninpawnee thread starter macrumors newbie

    Jun 9, 2015

    but are you saying that I can get 1920x1080 from this 2012 MBA using Apple's own display preferences (with presumably no performance penalty)? Or I need SwitchResX to do it (and perhaps with a penalty)?
  4. motrek macrumors 68020

    Sep 14, 2012
    Monitors accept all sorts of input signals and then scale the image up to fit the screen as necessary. You can drive a 4K monitor @ 1080p the same exact way you would drive a monitor that's 1080p natively, and with the same exact performance.
  5. roninpawnee thread starter macrumors newbie

    Jun 9, 2015
    final questions :

    1. if my MBA outputs 1920x1080 to the 4K monitor, would things seem any sharper on the 4K than it would on a 1080p monitor of the same size?

    2. if I get a new MBA 2015 and drive the 4K at 1920x1080, would things seem any sharper on the 4K ?

    I think all the menus will seem too small at the native 4K resolution.. so my question is - is there any benefit to a 4K monitor for me since I will run it at a lower resolution anyway? Will things seem sharper?
  6. motrek macrumors 68020

    Sep 14, 2012
    The 1080p signal coming out of one MacBook is going to be the same as the 1080p signal coming out of any other MacBook, or any other device or computer for that matter (phone, cable box, etc.).

    All the monitor sees is a 1080p signal, it doesn't know or care what's generating it.

    What the monitor does with it depends on the specific model of monitor. It might display each incoming pixel as a solid block of 2x2 pixels of the same color, in which case there's essentially no difference between a 4K monitor and a 1080p monitor.

    Depending on the monitor, it might do "upsampling" which means it will try to "guess" good colors for each pixel to show the input image in a smoother or sharper way (or both).

    Remember that upsampling doesn't actually work with any extra image information, so all those intermediate pixel values are just guesses, and they're going to be wrong a lot of the time. It will often blur stuff that should be sharp, or vice versa. This might look fine for TV and movies but I suspect it would look pretty bad for typical computer screen images.

    So, if you buy a 4K monitor and send it a 1080p image, I think there are two likely outcomes. Either the image quality is just as good as a 1080p monitor, or it will likely be worse to some degree.

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5 June 9, 2015