I was putting up some wall decorations earlier today and was painstakingly realigning everything until it looked level to my eyes. It might be just a hair off, but if I don’t correct it, I’ll see the misalignment almost instantly and get bothered for the rest of time until I fix it. Has anyone investigated, or is there literature on the minimum perceptible angle from level to the naked eye?
Yep, what we consider to be level is relative to what you use to establish an axial plane.