photopia

The 1931 CIE photopic luminosity function. The horizontal axis is wavelength in nm.

Photopic 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.

The human eye uses three types of cones to sense light in three respective bands of color. The biological pigments of the cones have maximum absorption values at wavelengths of about 420 nm (blue), 534 nm (Bluish-Green), resp. 564 nm (Yellowish-Green). Their sensitivity ranges overlap to provide vision throughout the visible spectrum. The maximum efficacy is 683 lumens/W at a wavelength of 555 nm (green).^[1]

The human eye uses scotopic vision under low-light conditions, and mesopic vision in intermediate conditions.

See also

• Candela
• Purkinje effect
• Photometry
• Photosensitive ganglion cell
• Scotopic vision

References

1. ^ Pelz, J. (1993). Leslie D. Stroebel, Richard D. Zakia. ed. The Focal Encyclopedia of Photography (3E ed.). Focal Press. p. 467. ISBN 0240514173. http://books.google.com/books?id=CU7-2ZLGFpYC&pg=PA467&dq=683+luminous+efficacy&ei=n3yvR_mrCJGgygSI2-ydBg&ie=ISO-8859-1&sig=cn1Fw0s76sQo2H7BhMyhuzmEc8E#PPA467,M1. 

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