xavito
Everything is related to the limitation of the resolving ability of the human eye - in 100% of sight (healthy person), it is about an angular minute.
1' = (1/60)° which is ≈ 2,9088821x10-4 rad
Such an angular size has the pixel on a television with a picture aspect (Aspect Ratio): 1.78: 1 (16: 9):
- 65 "SUHD (7680x4320) TV from a distance of 65 centimeters,
- 65 "UHD (3840x2160) TV from a distance of 1 meter and 29 centimeters,
- 65 "FHD (1920x1080) TV from a distance of 2 meters and 58 centimeters.
With three meters distance and normal viewing, neither on either TV will see individual pixels. So what's the meaning of the bigger resolution if even the FHD does not see everything up to the last pixel?
(on a UHD screen instead of a pixel there will be 4 pixels, and they will show some little detail. Does it make sense if the eye itself is unable to distinguish it from this distance?)
At a distance of up to two meters, things are different - the difference in the transition to a UHD resolution display will be noticeable. And when the difference is only visible if it is very good to see (yes, and in direct comparison - guess who, what is, it also makes no sense). There is only meaning when there is a clear improvement in detail, and not just the fact that UHD resolution is on the screen (here the little detail can be seen closely, and from three meters you need to know where to watch to see something similar to detail).
https://en.wikipedia.org/wiki/Optimum_HDTV_viewing_distance
THX ideal recommended distance
THX claims that the optimal viewing distance is a position / distance in which the display takes a 40 degree viewing angle (the angle between the vertical boundaries of the display and your eye), and the maximum viewing distance is approximately 28 degrees.
[TABLE="class: wikitable, width: 430"]
[TR]
[TH="bgcolor: #EAECF0, align: center"]
Screen Size[/TH]
[TH="bgcolor: #EAECF0, align: center"]
Recommended Range[/TH]
[/TR]
[TR]
[TD]35"[/TD]
[TD]1.0 m - 1.5 m[/TD]
[/TR]
[TR]
[TD]40"[/TD]
[TD]1.2 m - 1.8 m[/TD]
[/TR]
[TR]
[TD]50"[/TD]
[TD]1.5 m - 2.2 m[/TD]
[/TR]
[TR]
[TD]60"[/TD]
[TD]1.8 m - 2.7 m[/TD]
[/TR]
[/TABLE]
SMPTE ideal recommended distance
The SMPTE guidelines recommend that you sit at a distance where the screen fills up about 30 degrees from your visual field, as a minimum for a good experience. This usually gives good results. But viewers who use their TVs primarily to watch movies can take advantage of sitting a little closer to gaining a more theatrical experience. The reference recommendation of SMPTE for cinemas is about 40 degrees.
https://www.omnicalculator.com/other/tv-size-distance
https://stari.co/tv-monitor-viewing-distance-calculator
http://www.displaywars.com/