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Spectral sensitivity is the relative efficiency of detection, of light or other signal, as a function of the frequency or wavelength of the signal. In visual neuroscience, spectral sensitivity is used to describe the different characteristics of the photopigments in the rod cells and cone cells in the retina of the eye.
The luminous flux, which is also a photometric quantity, represents the light power of a source as perceived by the human eye. The unit of luminous flux is the lumen (lm). It is defined as follows: a monochromatic light source emitting an optical power of (1/683) watt at 555 nm has a luminous flux of 1 lumen (lm).
The spectral sensitivity function of the average human eye under daylight conditions (photopic vision) is defined by the CIE spectral luminous efficiency function V(λ). Only in very rare cases, the spectral sensitivity of the human eye under dark adapted conditions (scotopic vision), defined by the spectral luminous efficiency function V'(ë), becomes technically relevant.
- Luminosity Function For Photopic Vision
- Luminosity Function For Scotopic Vision
- Determination of Luminosity Functions
- Applications of Luminosity Functions
- Luminosity Functions of Galaxies
- More to Learn
For photopic vision, i.e., at sufficiently highlighted levels, the human eye uses the cone receptors, of which it has three different kinds (L, M and S). Their output signals are combined to determine the total received brightness. In the simple case of monochromatic light with some wavelength λ, the luminous flux produced by a light source can be ...
Scotopic vision occurs at low light levels, where only the rod photoreceptors are involved because the cones are unable to provide sufficiently strong signals. In this regime, a different luminosity function called V′(λ)(defined by CIE in 1951) must be applied. That function is peaked at 507 nm, and is again normalized to be unity at that point. Th...
For determining luminosity functions, relatively complicated procedures are required, where it is tested how a larger group of individuals reacts to certain types of optical stimulus. One of the used methods is heterochromatic flicker photometry. Here, one essentially adjusts the relative powers of two signals with different wavelengths, to which t...
Based on the known luminosity functions and the known optical spectrum of a light source, one can calculate how bright a light source or an illuminated object can be perceived. For example, that allows one to calculate the luminous efficacy and efficiencyof a light source if its efficiency for the conversion from electrical power to light power is ...
An entirely different meaning of the term luminosity function is used in astronomy. With optical telescopes and specific photodetectors, one measures luminosities (in the sense of spectral intensities) of many galaxies for different spectral bands. One can then define a luminosity function which reflects the number distribution of many galaxies ove...
Encyclopedia articles: 1. photometry 2. luminous flux 3. luminous efficacy and efficiency 4. luminosity 5. chromaticity
A luminous efficiency function or luminosity function represents the average spectral sensitivity of human visual perception of light. It is based on subjective judgements of which of a pair of different-colored lights is brighter, to describe relative sensitivity to light of different wavelengths. It is not an absolute reference to any ...
The human eye is sensible to light wave which wavelength is roughly between 400 nm (violet) and 700 nm (red). Wavelengths shorter than 400 nm (ultraviolet, UV) or longer than 700 nm (infrared, IR) are not visible. The eye behaves differently in high or low light conditions: in daylight, for brightness levels above 3 cd/m 2 the vision is mainly ...
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What is the spectral sensitivity function of a human eye?
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The spectral sensitivity function of the average human eye under daylight conditions (photopic vision) is defined by the CIE spectral luminous efficiency function V(λ). Only in very rare cases is the spectral sensitivity of the human eye under dark adapted conditions (scotopic vision), defined by the spectral luminous efficiency function V'(λ), technically relevant.
