Mind Hacks

Hack #14. See the Limits of Your Vision

The high-resolution portion of your vision is only the size of your thumbnail at arm’s length. The rest of your visual input is low res and mostly colorless, although you seldom realize it.

Your vision isn’t of uniform resolution. What we generally think of as our visual ability, the sharpness with which we see the world, is really only the very center of vision, where resolution is at its highest. From this high-resolution center, the lower-resolution periphery, and using continual movements of our head and eyes [[Hack #15]], we construct a seamless—and uniformly sharp—picture of the universe. But how much are we compensating? What is the resolution of vision?

The eye’s resolution is determined by the density of light-sensitive cells on the retina, which is a layer of these cells on the back of the eye (and also includes several layers of cells to process and aggregate the visual signals to send on to the rest of the brain). If the cells were spread evenly, we would see as well out of the corners of our eyes as directly ahead, but they’re not. Instead, the cells are most heavily packed right in the center of the retina, a small region called the fovea, so the highest-resolution part of the vision is in the middle of your visual field. The area corresponding to this is small; if you look up at the night sky, out of everything you see, your fovea just about covers the full moon. Away from this, in your peripheral vision, resolution is much coarser. ...