The Human Retina - Explained in 90 Seconds
The "rod" cells in the retina can detect a single photon. These cells are responsible for peripheral vision and low light vision. They provide black/white/grey vision and cannot detect color.
Special proteins in the cells can absorb an individual photon and as a result change the cell's membrane potential enough to trigger the cell.
The retina contains about 100 million rod cells.
The "cone" cells in the retina provide color vision. The retina has about 6 million cone cells and almost all are concentrated in a tiny "dimple" on the retina called the macula. It's only a few mm wide. This minuscule structure gives us our central field vision and our color vision!!!!!
Cone cells can detect frequency of light and there are 3 types of cones, each sensitive to a different frequency range. The "B" cones are most sensitive to blue, the "G" cones are most sensitive to green and the "R" cones are most sensitive to red. So our color vision is called "tricolor vision". By comparing outputs from the 3 cell types the brain "mixes" the 3 color signals to detect any color!
Content written and posted by Ken Abbott firstname.lastname@example.org