Question: hwo do rods and cones work and what is the difference between a rod and a cone?

Steven Gardner answered on 27 Jun 2013:

Rods and cones detect light in slightly different ways. The way rods do it is more efficient but also makes them unable to distinguish between different colours. Rods are more used from peripheral and low-light vision. Cones need more light to work but can distinguish colours. So they concentrate at your fovea (the part where you have your sharpest central vision). There are some cones in the outer part of the eye, but also the brain itself might be involved in ‘filling in’ the colour of things in your peripheral vision based on experience (it’ll fill in a blue sky and green grass for instance).