The smallest pattern that is able to distinguish the human eye

Research has shown that the sharpness of our limited ability to distinguish about 120 pixels per angular degree. For example, you need to take placed at arm's length with the subject area of ​​the nail, with put on it 60 horizontal and 60 vertical lines alternately white and black, like a chess board. It is the fine pattern, which is still able to distinguish the human eye.

via www.bbc.com/russian/science/2015/08/150804_vert_fut_limits_of_human_vision