It's also a biological fact that from a distance of about 25 feet and beyond the human eye is already focused at infinity. Therefore, it makes absolutely zero difference if the target is 20 yards, 40 yards or or even farther away. There is nothing, I repeat, nothing that one can do to change the eyes focus beyond this point. One can look very intently at the target and concentrate very hard on the target( mistakenly termed focus ) but you cannot change the focus of the eye that has already automatically been performed by your brain and eyes. This assumes one has normal vision or is corrected to normal vision....emmetropia.
