Humans normally have three kinds of cones. The first responds the most to light of long wavelengths, peaking at a reddish colour; this type is sometimes designated L for long. The second type responds the most to light of medium-wavelength, peaking at a green colour, and is abbreviated M for medium. The third type responds the most to short-wavelength light, of a bluish colour, and is designated S for short. The three types have peak wavelengths near 564–580 nm, 534–545 nm, and 420–440 nm, respectively. The difference in the signals received from the three cone types allows the brain to perceive all possible colours, through the opponent process of colour vision. (Rod cells have a peak sensitivity at 498 nm, roughly halfway between the peak sensitivities of the S and M cones.)
All of the receptors contain the pigment photopsin, with variations in its conformation causing differences in the optimum wavelengths absorbed.
The colour yellow, for example, is perceived when the L cones are stimulated slightly more than the M cones, and the colour red is perceived when the L cones are stimulated significantly more than the M cones. Similarly, blue and violet hues are perceived when the S receptor is stimulated more than the other two.
The S cones are most sensitive to light at wavelengths around 420 nm. However, the lens and cornea of the human eye are increasingly absorptive to shorter wavelengths, and this sets the short wavelength limit of human-visible light to approximately 380 nm, which is therefore called 'ultraviolet' light. People with aphakia, a condition where the eye lacks a lens, sometimes report the ability to see into the ultraviolet range. At moderate to bright light levels where the cones function, the eye is more sensitive to yellowish-green light than other colors because this stimulates the two most common (M and L) of the three kinds of cones almost equally. At lower light levels, where only the rod cells function, the sensitivity is greatest at a blueish-green wavelength.
Cones also tend to possess a significantly elevated visual acuity because each cone cell has a lone connection to the optic nerve, therefore, the cones have an easier time telling that two stimuli are isolated.
Read more about this topic: Cone Cell
Other articles related to "types, type":
... General aviation involves a wide range of aircraft types such as Business jets, trainers, homebuilt, aerobatic types, racers, gliders, warbirds, firefighters and medical transports ... The vast majority of aircraft today are general aviation types ...
... Claw-types set quickly in most seabeds and although not an articulated design, they have the reputation of not breaking out with tide or wind changes, instead slowly turning ... Claw types have difficulty penetrating weedy bottoms and grass ... ratio and generally have to be oversized to compete with other types ...
... Arquilla and Ronfeldt point to three basic types of networks that may be used by netwar actors Chain network – typified by smuggling networks, where end-to-end exchanges (information, contraband, etc ... Netwar actors may also take on hybrid forms as well, blending different types of networks and hierarchies ... networked to each other through different types of network structures ...
... Attempts to introduce types date back to the 1980s, and as of 2008 there are still attempts to extend Prolog with types ... Type information is useful not only for type safety but also for reasoning about Prolog programs ...
... The principal types of graphemes are logograms, which represent words or morphemes (for example, Chinese characters, or the ampersand representing the English word and also Arabic numerals) syllabic characters ... For a full discussion of the different types, see Writing system Functional classification of writing systems ...
Famous quotes containing the word types:
“Our major universities are now stuck with an army of pedestrian, toadying careerists, Fifties types who wave around Sixties banners to conceal their record of ruthless, beaverlike tunneling to the top.”
—Camille Paglia (b. 1947)
“Hes one of those know-it-all types that, if you flatter the wig off him, he chatter like a goony bird at mating time.”
—Michael Blankfort. Lewis Milestone. Johnson (Reginald Gardner)
“Our children evaluate themselves based on the opinions we have of them. When we use harsh words, biting comments, and a sarcastic tone of voice, we plant the seeds of self-doubt in their developing minds.... Children who receive a steady diet of these types of messages end up feeling powerless, inadequate, and unimportant. They start to believe that they are bad, and that they can never do enough.”
—Stephanie Martson (20th century)