How can people distinguish edges of objects? Is this a function of rods or cones, or some organs else?
We detect the presence of edges when the light detected by our rods and cones changes abruptly across space (location on our retina) or time (due to our eyes moving). These changes in light intensity are what produce the signals ultimately transmitted to our brains and interpreted as objects (defined by their edges). So, yes, it is a function of our rods and cones with our cones being a little bit better at it than rods.
