Human photoreceptors are of three types: Rods (sensitive to violet and low intensity light), and red-, green-, or blue-sensitive cones. Cone cells require brighter light than rod cells to function
Rods and Cones
Human photoreceptors are of three types: Rods (sensitive to violet and low
intensity light), and red-, green-, or blue-sensitive cones. Cone cells require
brighter light than rod cells to function
The pixels (picture elements) found on a color TV screen are also of three
types: red, green, or blue.
All the colors of the spectrum can be produced with combinations of the red, green, and blue cone cells
Relative quantity of rods and cones as you move from the fovea to the peripheral vision. Note that the proportion of rods increases as you move to the peripheral area. The proportion of cones is greatest at the fovea. The actual density of photoreceptors in general decreases as you move away from the fovea and both rods and cones are absent at the blind spot.
Dogs are red-green colorblind. They see a washed-out but brighter color image as shown above.
The visual acuity (sharpness) of dog vision is less than ours since they don't have a fovea. The reason dogs look you straight in the eye is a behavioral modification.
Dogs see better at night since they have more rod cells and a reflective layer behind the retina called the tapetum lucidum.
Dogs can see movement better than us.
Dog peripheral vision is better than ours (the yellow areas in the above diagram).
The area for dog depth of field is less than ours (blue area). Stereoscopic vision is in the area of the visual field where both eyes overlap.
The field of view for a dog is greater than ours (total visual field). They can see objects almost behind them!
Cat color vision is poorer than dogs since they rely almost entirely on rod cells for their vision (compare cat to "rods only").
The visual acuity of cats is much greater than ours, even though they don't have a fovea. This is because their rod cells are more densely packed than our photoreceptors.
Cats see better at night since they have more rod cells and a reflective layer behind the retina called the tapetum lucidum. Compare the views in the above images.
Cats see movement better than we do.
Cat peripheral vision is similar to ours.
The depth of field, stereoscopic vision, and field of view for cats is similar to ours.
Cats can not see in the dark. Compare the above images.
