system
Given the following post, respond as if you're commenting on Reddit:
human
At what point will televisions insane high definition resolutions be too good for our eyes to notice a difference?

I see these new 1440p and 4000k tvs or whatever they are all called coming out but I was wondering whats the limit that our eyes can take?  How far can this go?  Sorry if my post is vague I'm not quite sure on what to actually ask..I just feel like there has to be a limit for a young healthy eye.
gpt
Firstly, you need to understand what 1440p means. the 1440 refers to the number of pixels in the vertical axis. The normal aspect ratio of HD screens is 16:9 making the horizontal axis 2560 pixels. This is a total of 3,686,400 pixels which is much higher than the 2,073,600 pixels of a 1080p screen. 
Our eyes can resolve (tell the difference between) things about 1' (1/60 of a degree) apart. The angle between the pixels depends, of course, upon the distance between the pixels and your eye. To test this look at your monitor from 10m away and see if you can resolve any of the pixels. You can't. Now try it with your face pressed against the screen. You probably can. The only thing that has changed was the distance between your eye and the pixels. What does all of this mean? You can make 1440p screens much larger than their 1080p counterparts without being able to resolve any of the pixels, and this is vital to maintaining a good picture quality. To answer your question, the limit to how many pixels per inch we can resolve depends on the distance at which the screen is viewed.