Editing Luminous efficiency function (section)

==Scotopic luminosity==
For very low levels of intensity ([[scotopic vision]]), the sensitivity of the eye is mediated by rods, not cones, and shifts toward the [[violet (color)|violet]], peaking around {{nowrap|507 nm}} for young eyes; the sensitivity is equivalent to {{val|1699|u=lm/W}}<ref name="Kohei2004"/> or {{val|1700|u=lm/W}}<ref name="Casimer1998"/> at this peak. The standard scotopic luminous efficiency function or ''V''{{′}}(''λ'') was adopted by the CIE in 1951, based on measurements by Wald (1945) and by Crawford (1949).<ref>{{Cite web|url=http://www.cvrl.org/database/text/lum/scvl.htm|title=Scotopic luminosity function}}</ref>

Luminosity for [[mesopic vision]], a wide transitioning band between scotopic and phototic vision, is more poorly standardized. The consensus is that this luminous efficiency can be written as a weighted average of scotopic and mesopic luminosities, but different organizations provide different weighting factors.<ref name="visual3d">[http://www.visual-3d.com/Education/LightingLessons/Documents/PhotopicScotopiclumens_4%20_2_.pdf Photopic and Scotopic lumens - 4: When the photopic lumen fails us]</ref>