"Deconvolution in humans

A huge fraction of our brain is devoted to vision. One of the neglected features of our visual system is that the raw image falling on the retina is severely blurred: while most people can see with a resolution of about 1 arcminute (one sixtieth of a degree) under any daylight conditions, bright or dim, the image on our retina is blurred through a point spread function of width as large as 5 arcminutes (Wald and Grison, 1947; Howarth and Bradley , 1986). It is amazing that we are able to resolve pixels that are twenty-five times smaller in area than the blob produced on our retina by any point source. Isaac Newton was aware of this conundrum. It's hard to make a lens that does not have chromatic aberration, and our cornea and lens, like a lens made of ordinary glass, refract blue light more strongly than red. Typically our eyes focus correctly for the middle of the visible spectrum (green), so if..."

I recommend the read for those interested. There's even an experiment you can do yourself to experience your own eyes limitations!