For example:
- 40 cm view distance (e.g. smartphone): 300 ppi is roughly the maximum that's useful
- 100 cm (e.g. desktop monitor): about 200 ppi
https://www.nature.com/articles/s41467-025-64679-2/figures/2
Put another way look at 300ppi prints and 1200ppi prints. The difference is night and day at 30 cm viewing.
You don't need 1200ppi for a nice 1200dpi print; even 300ppi may be enough.
On the other hand, for printing text, an 1200 dpi printer has the quality of an 1200 ppi printer.
Many well-designed traditional typefaces have relied on optical effects caused by details that require for being printed a resolution higher than that at which the human eye can distinguish a set of bars from an uniform background (which is the object of TFA). For instance, in some typefaces the edges of the strokes are concave or convex, not straight, which could be rendered in a computer display only by either a much higher resolution or by more sophisticated pixel preprocessing methods (in order to simulate the effect on the eye). Whenever such typefaces are displayed at a lower resolution, i.e. on computer monitors, they are very noticeably uglier than when printed on paper by traditional metal printing methods or even by a high-resolution laser printer.
A 27" monitor has a height around 17", i.e. about 43 cm, and for watching a movie or anything else where you look at the screen as a whole the recommended viewing distance is twice the screen height, i.e. about 86 cm.
At this distance, the resolution needed to match the human vision is provided by a height of slightly less than 3000 pixels by this study, but by about 3300 pixels by older studies. In these conditions you are right, the minimum acceptable resolution is around 200 ppi.
This means that a 27 inch 5k monitor, with a resolution of 2880 by 5120 pixels, when viewed from a distance twice its height, i.e. about 86 cm (34 inch), provides a resolution close, but slightly less than that of typical human vision. (That viewing distance that is double the height corresponds to the viewing angle of camera lenses with normal focal length, which has been based on studies about the maximum viewing angles where humans are able to perceive a correct perspective when looking at an image as a whole.)
However, when not watching movies, but working with text documents, you normally stay closer to the monitor than that, so even a 5k monitor is not good enough (but an 8k monitor may be enough, so that might be the final monitor resolution, beyond which an increase is useless).
Size increases, animation decreases (when your iPhone is getting old, turn off animation and behold it operating super fast!), etc can all be found there.
I zoom websites until they "feel right" which is usually something close to "they are as wide as the window I have them in" - HN is a few taps up from "actual size".