Experts say tech fans with an endless desire for a sharper resolution are sometimes paying for more pixels than their eyes can actually see. A person's field of vision covers about 200 degrees, a little more than a semicircle. At arm's length their index finger's fingernail will appear to be about the width of one of those degrees. Imagine that fingernail covered in 120 alternating black and white stripes — being able to discern those stripes at that distance is just about the theoretical limit of the human eye. But in reality, hardly anyone has such superb vision. In fact, most people would be unable to discern pixels or lines twice that size. And whether a phone or tablet display meets that standard depends on how far it it is from the viewer. In a living room, a viewer's 40- to 60-inch TV is positioned at a fixed distance, probably seven to nine feet away. Unless pixel-hungry TV fans buy far larger set, or push their couches much closer, any increases in resolution simply won't be perceived.