A few days ago I was talking with a friend of mine about screen resolutions. From Torvald’s complaint about low screen resolutions in laptops nowadays to smartphone screens, etc. I’ve read several times that someone with 20/20 perfect vision can’t see with much more definition than one minute of arc. Or, according to Wikipedia, someone with 20/20 vision should not be able to tell two objects apart if together they cover less than one arcminute of their field of view.
If that’s true, it’s very easy to create a Pixel Visibility Calculator that, given a screen size, resolution and distance, can tell you if you should be able to see the pixels or not. For that, you need to calculate how big the pixel diagonal is. If two pixel diagonals are bigger than one arcminute, your eye could in theory tell them apart. I’m not sure if that’s enough to say that you’ll see the pixels, but let’s use it as a worst case scenario.
According to the calculator, I can watch my 46" 1080p TV from two meters and a half away and and I wouldn’t be able to see the pixels even if I had perfect vision, which I don’t have. Despite that, some manufacturers already have 2160p TVs in mind. It looks like the upgrade won’t be worth it. :)