Cones

Cones are a special type of light-sensitive cell located on the retina, which are able to absorb light under high levels of illumination. Most people have 3 types of cones sensitive to (or able to absorb) light with a range of Short, Middle-length and Long wavelengths. These are abbreviated as the S-cones, M-cones and L-cones respectively.

The relative amounts of light absorbed by each type of cone are compared to give colour information about objects.

The graph shown plots the relative sensitivity for each cone type shown on the y-axis, for each wavelength shown on the x-axis. The sensitivity relates to the amount of light that each cone type can absorb at each wavelength. Each cone type absorbs light over a wide range of wavelengths. Note that one nanometer is one billionth of a meter.

Relative sensitivities of the three types of cones, sensitive to short (S), middle (M) and long (L) wavelengths. Image adapted from R.W. Pridmore (see Figure 1 - Atten Percept Psychophys (2021) 83:1 797–1803).

See also: Parts of the Eye.