This is the vision as captured by the fovea. Most of the photoreceptors there are cones and practically every cone has its own nerve to the brain. Therefore the image is sharp and in colour. The whole eye is built to project the image sharp (in focus) onto the fovea. |
The remainder but largest part of the retina is covered by the rods which are light sensitive but not colour sensitive. In fact, the rods are more light sensitive than the cones. For example, at night when you are outside, and you look at a faint star, you may see it better when you don't look at it straight but at a slight distance from the star. |
The rods in the peripheral retina, and the nervous system attached to them, are especially sensitive to movements. Therefore, when something moves, in the "corner" of the eye, it attracts our attention, we turn our eye towards the source of the movement and see it sharp and in colour. |
In some patients, who have their peripheral vision destroyed, the lack of a peripheral vision is striking. They can still see clearly and in colour with their fovea but they are often involved in road accidents, as they have not seen other cars moving into their path from other directions. They lack an early warning system. |