The 1931 CIE<unk>  luminosity function. The horizontal axis is wavelength in nm.<unk>  is the vision of the eye under well-lit conditions (luminance level 10 to 108 cd/m2). In humans and many other animals,<unk>  allows color perception, mediated by cone cells, and a significantly higher visual acuity and temporal resolution than available with scotopic vision. The human eye uses three types of cones to sense light in three bands of color. The biological pigments of the cones have maximum absorption values at wavelengths of about 420 nm (blue), 534 nm (bluish-green), and 564 nm (yellowish-green). Their sensitivity ranges overlap to provide vision throughout the visible spectrum. The maximum efficacy is 683 lm/W at a wavelength of 555 nm (green). By definition, light at a frequency of hertz has a luminous efficacy of 683 lm/W. The wavelengths for when a person is in<unk>  vary with the intensity of light. For the blue-green region (500 nm), 50% of the light reaches the image point of the retina. Adaptation is much faster under<unk> ; it can occur in 5 minutes for<unk>  but it can take 30 minutes to transition from<unk>  to scotopic. Most older adult humans lose<unk>  spatial contrast sensitivity. Adults in their 70s require about three times more contrast to detect high spatial frequencies than adults in their 20s. The human eye uses scotopic vision under low-light conditions (luminance level 10−6 to 10−3.5 cd/m2), and mesopic vision in intermediate conditions (luminance level 10−3 to 100.5 cd/m2).
Photopic vision
Scotopic vision
Mesopic vision
Monocular vision
Binocular vision
Retinal summation
Visual temporal integration
Color vision