Comment by perching_aix

> 3-6m from your TV (...) lets you "cheat" with ordinary TV sizes (50"-65") because you will not or barely notice the difference between 1080p and 2160p.

Yes, at those sizes and distances, all the usual rules of thumb will report that the difference will be indistinguishable between FHD and UHD. We're in agreement there.

It's just that if "cinematic immersion" is among the goals at all, I really don't think e.g. viewing a 50" TV from 6 meters away can provide it. That's more like "something is making noise while I'm having a pop and scrolling social media on my phone" at best. A lot of TV watching happens like that, but then resolution is rarely a concern during those anyways.

> You usually sit 60cm from your monitor

> the 'retina' effect

So we're selecting for 60 PPD ("retina") at 60 cm of viewing distance, let's see:

21" -> 42.352° hfov, 2544 × 1431, ~139 PPI. At UHD, it's ~210 PPI. WQHD would be enough though, and that'd be ~140 PPI.

22" -> 44.18° hfov, 2656 × 1494, ~139 PPI. At UHD, it's ~200 PPI.

23" -> 45.981° hfov, 2768 × 1557, ~138 PPI. At UHD, it's ~192 PPI.

24" -> 47.761° hfov, 2880 × 1620, ~138 PPI. At UHD, it's ~184 PPI.

25" -> 49.52° hfov, 2976 × 1674, ~137 PPI. At UHD, it's ~176 PPI.

26" -> 51.25° hfov, 3088 × 1737, ~136 PPI. At UHD, it's ~169 PPI.

27" -> 52.96° hfov, 3184 × 1791, ~135 PPI. At UHD, it's ~163 PPI.

All of this is to say, I have no idea where you're pulling that ~220 PPI figure from, especially when it comes to higher sizes.

You can also see the PPI slowly descending from some maximum value (eventually reaching 0) since we're talking about a flat panel, and so the math slowly gives out. If you assume a curved display and make the viewing distance the curvature radius (600R) to compensate, you can calculate that maximum value to be ~145.5 PPI. In that case, this value would remain fixed no matter the diagonal size. Not anywhere close to 220 PPI still however.

That said, I definitely sit further than 60 cm too.