Scotopic vision is the vision of the
eyeEyes are organs that detect light, and send electrical impulses along the optic nerve to the visual and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system...
under low light conditions. The term comes from Greek
skotos meaning
darkness and
-opia meaning
a condition of sight. In the human eye cone cells are nonfunctional in low light - scotopic vision is produced exclusively through rod cells so there is no color perception. Scotopic vision occurs at
luminanceLuminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle. The SI unit for luminance is candela per square...
levels of 10
-2 to 10
-6 cdThe candela is the SI base unit of luminous intensity; that is, power emitted by a light source in a particular direction, weighted by the luminosity function...
/m². In other life forms, such as the Elephant Hawk-moth (
Deilephila elpenor), advanced color discrimination
is displayed.
Mesopic visionMesopic vision is a combination of photopic vision and scotopic vision in low but not quite dark lighting situations.The combination of the higher total sensitivity of the rods in the eye for the blue range with the color perception through the cones results in a very strong appearance of blue-ish...
occurs in intermediate lighting conditions (
luminanceLuminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle. The SI unit for luminance is candela per square...
level 10
-2 to 1
cdThe candela is the SI base unit of luminous intensity; that is, power emitted by a light source in a particular direction, weighted by the luminosity function...
/m²) and is effectively a combination of scotopic and photopic vision. This however gives inaccurate visual acuity and colour discrimination.
In normal light (
luminanceLuminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle. The SI unit for luminance is candela per square...
level 1 to 10
6 cdThe candela is the SI base unit of luminous intensity; that is, power emitted by a light source in a particular direction, weighted by the luminosity function...
/m²), the vision of cone cells dominates and is
photopic visionPhotopic vision is the vision of the eye under well-lit conditions. In humans and many animals, photopic vision allows color perception, mediated by cone cells....
. There is good
visual acuityVisual acuity is acuteness or clearness of vision, especially form vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain....
(VA) and colour discrimination.
In scientific literature, one occasionally encounters the term scotopic lux which corresponds to photopic lux, but uses instead the scotopic visibility weighting function.