At what point do we as humans stop telling the difference?

DullGreyGuy

jshm2 said:

It's actually more than just display, it's sound and scale as well. You will notice little difference between 1080 and 4k on a 35" HD ready screen, But try and watch that content on a 8k or 12k screen and it will be very evident. 

But the sound quality is also part of the package - as is the size of the screen. 

A "HD Ready" screen would be a 720 rows. You should see no difference at all if you presented it with 1080 or 2160 (4k) because they'd have to be downscaled to 720 rows. 

If you were to put 1080 or 2160 through a 35" screen and sat the normal 2-4m away from the screen it would make no difference at all if the screen was HD, 4K, 8K or 12K because the pixel size in all 4 would be too small for you to see the difference at that distance. You probably could tell the difference between HD Ready (720) and HD (1080)

MattMattMattUK

Not all 4K is created equally, bitrate also makes a huge difference, as does encode, source, display etc. Some 4k feeds, particularly from streaming services contain minimally more data than the 1080p feed. 

If one compares a 1080p Blu-Ray, with a 4k UHD-Blu-Ray then even at TV viewing distances the difference is noticeable, especially in higher contrast scenes, very dark scenes or scenes with high speed motion. Now the bit rate on a 4k UHD Blu-Ray can go up to 128Mbps, where as for a Netflix 4K stream it tops out at 4Mbps for almost everything (there are a few thing that will stream at 8 or 16, but that is less than 1% of all content and nothing new added in the last two years has been higher than 4Mbps. 

Edit to add: I can tell the difference between 1080p and 4k at normal TV viewing distances easily, even more so at PC monitor viewing distances. I have only seen 8k content on an 8k screen twice and I could not tell the difference between 4k and 8k on a TV screen at a distance, up close it was discernible. For a monitor it was a visible difference if looking for it, but I think in normal usage one would be hard pressed to tell the difference.