Spectral sensitivity of the human eye

Intro

It is the relative efficiency of detection of light or other signal, as a function of the frequency or wavelength of the signal.
 * What is "Spectral sensitivity"?

And there are two types of retinal photo-receptors exist.
 * Cones cell -> responding to bright-light condition (Photopic vision). And these cells concentrated in the center of the retina.
 * Rod cell -> responding to low-intensity light condition (Scotopic vision).

Depending on their spectral sensitivity, belong to
 * Long-wavelengths sensitive (L)
 * Mid-wavelengths sensitive (M)
 * Short-wavelengths sensitive (S)

Spectral sensitivity of eye is influenced by light intensity.

Light intensity determines
 * The level of activity of cones & rods.
 * Main characteristic of human vision

Visible spectrum
 * visible spectrum means sensitivity of cones & rods. It varies with the wavelength.
 * Wavelength ranges between 380 nm and 800 nm.

Sensitivity of human eye
 * Sensitivity of human eyes to light increase with the decrease in light intensity.
 * In day-light condition, the eye is most sensitive at 555 nm.
 * In darkness condition, the eye is most sensitive at 507 nm.

Conclusion
 * As light intensity decreases, cone function changes more effective way.
 * When decrease the light intensity, it prompt to accumulation of rhodopsin. Furthermore, in activates rods, it allows to respond to stimuli of light in much lower intensity.

Source : Gigahertz-optic : http://www.light-measurement.com/spectral-sensitivity-of-eye/ Wikipedia : http://en.wikipedia.org/wiki/Spectral_sensitivity Naver : http://endic.naver.com/enkrEntry.nhn?entryId=59b4cdfcbb25434ba38c5c79f0d3c82f Naver : http://terms.naver.com/search.nhn?query=spectral+sensitivity&where=&x=0&y=0