To Retina or not to Retina (On an external monitor)

[abhi182]

If you use a Mac with an external high res monitor in scaled mode, all retina modes are effectively done by the GPU running at 2x the desired "looks like resolution" (e.g. GPU rendering at 5120X2880 for a looks like 2560X1440 setting) EXCEPT the native resolution of the monitor

i.e. On a 4K monitor the looks like 1920X1080 mode has the GPU running at 3840x2160 , looks like 2560x1440 has GPU at 5120X2880
But
at the native resolution (i.e. 3840x2160),, the GPU actually renders at 3840x2160

So this got me thinking

I am presuming that an optimal PPI is the quest i.e. as long as the PPI is above a certain threshold (e.g. say 110 for a desktop monitor/ 150 for a laptop monitor- since it is normally held closer to the eye), the text rendering will appear nice & crisp.

So given the above, Would there be a perceivable difference, if any, if you use:

a) A high res (4K) display doing the said 2X render and subsequently compressed
vs
B) A lower res (say QHD) display running at native resolution without the 2:1 compression

For context, I am thinking of upgrading my existing 4K 24" monitor - that I do love at 110 dpi (looks like 2304x1296 hiDPI resolution) - with a larger display
However I am not entirely sure now if I should get a larger 4K display (and set it to say 2560x1440) or simply get a QHD and run it at native res while ensuring the PPI is around the existing 110 or so

Edit: We still have a corona lockdown in my country so trying it out in a store is not an option. sadly

 

[AlphaCentauri]

With BigSur, Retina only. Native resolutions look awful due to lack of proper font aliasing on non-retina monitors.

 

[mj_]

For context, I am thinking of upgrading my existing 4K 24" monitor - that I do love at 110 dpi (looks like 2304x1296 hiDPI resolution) - with a larger display

This right here is the flaw in your math. Your current 24" 4K display may be running at "looks like 2304x1296" but that doesn't mean it's displaying 110 dpi. It is still displaying native resolution, aka 3840x2160, which on a 24" display equals 183 dpi. Trust me, it would very very different (aka abysmal) if it were running at just 110 dpi.

 

[Amethyst1]

Would there be a perceivable difference, if any, if you use:

a) A high res (4K) display doing the said 2X render and subsequently compressed
vs
B) A lower res (say QHD) display running at native resolution without the 2:1 compression

Yes. There is a very noticeable difference. Even scaled, option A looks a lot better than B. I wouldn't even consider B.

 

[xraydoc]

I use a 32" 4K display at 'looks like' 3008x1692. Looks fantastic. On the M1, there is zero perceptible performance impact even though it's not 2:1.

 

[abhi182]

Thanks fellas - I have ordered a LG 32 UHD (32UD59)
Now to figure out what to do with the existing 24 UHD - lol