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I am using Retina Display Menu (RDM) to give me a higher resolution for my MBP, and the sweet spot that I have found is 1920x1080.

However I get 2 different display options for this resolution depending on the monitor I am connected to - Acer V243HQ (regular) resolution - Samsung U28E590D 28-Inch

However with the Samsung I get the attached where the resolution has a lighting bolt which actually shows the text well rendered

RDM Extra Menu - 1929 x 1080

My question is why does this happen only with specific monitors, and how can I get this even without having to plug my external monitor

UPDATE 1: Could it be that the Samsung has 4K support? could it be related to that?

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The lighting bolt icon indicates that it is a Retina (HiDPI) resolution.

Essentially when you're picking 1920x1080, a 1920x1080 resolution signal is generated and sent to the monitor. This is supported by both monitors.

When you pick 1920x1080 Lightning, in actual fact a 3840 x 2160 resolution signal is generated and sent to the monitor. This consists of the ordinary image, you're used to see - but magnified with a factor of 4 so it looks like 1920x1080 in physical size when rendered.

One of the notable exceptions is though that the text is actually rendered in the higher resolution with a higer font size, so it has the same physical size, but is "prettier" (i.e. less blurry/jagged).

You only get the Lightning choice with the Samsung monitor as it is the only of the two that supports a 4k (3840 x 2160) resolution.

  • Oh wow! Is there any way I can fake that effect even without having a 4K monitor connected? – Stephen Senkomago Musoke Jun 2 at 3:37
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    No, that’s not possible for an end-user scenario. You can enable fake HiDPi for developer debugging, but it is not usable in practice as everything on screen becomes four times bigger. – jksoegaard Jun 2 at 8:31
  • I found an app SwitchResX (madrau.com) with advice from the developer to fake this. 1. Create a scaled 3840x2160 resolution for all monitors you use, and you'll get this 1920x1080 HiDPI, but it will look at best on 4K monitor (or higher). 2. If you want to check, you can install SRX, it's free for 10 days; just install, disable SIP, and create a custom scaled resolution of 3840x2160 for your Asus. After a reboot, it should be available for you to choose. – Stephen Senkomago Musoke Jun 5 at 5:12
  • You don’t want to do that. Either you get a 4th if the visible area on screen, which you can get for free with the developer tool I mentioned, or you get the same visible area with no improvement in quality. Then you’re just burning CPU for no reason. – jksoegaard Jun 5 at 7:52
  • Once I added the 3840 x 2160 resolution, I got the HiDPI option for 1920x1080 which was what I wanted at the end – Stephen Senkomago Musoke Jun 5 at 11:12

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