Editing Luminous efficiency function (section)

=== Non-vision parameters ===

The wavelength-dependent effect of light is seen not only with vision, but also (in humans) in the [[circadian rhythm]] via [[melanopsin]]. For reporting the effect of light on the human circadian rhythm, a value called ''melanopic illuminance'' is used, defined using a luminous efficiency function specific to the melanopsin. The unit is lux (lx) used in a non-SI-compliant fashion. With CIE S 026:2018, the system has become SI-compliant, with the melanopic equivalent daylight illuminance (M-EDI, unit [[lux|lx]]) being derived from melanopic irradiance (unit W/m<sup>2</sup>). A human being subject to 100 lx of M-EDI of light should have the same alternation to their circadian rhythm as if they are being exposed to 100 lx of daylight.<ref name="LucasGroup">{{cite web |title=Measuring melanopic illuminance and melanopic irradiance |url=https://lucasgroup.lab.manchester.ac.uk/measuringmelanopicilluminance/ |website=Lucas Group}}</ref>

Lucas (2014) and the later CIE S 026 also define luminous efficiency function specific to four other human opsins. Lucas uses non-SI-compliant lux while CIE uses SI-compliant EDI lux.<ref name="LucasGroup"/> Although the CIE standard requires payment, the associated toolbox and its user guide is available for free.<ref>{{cite web |url=https://files.cie.co.at/CIE%20S%20026%20alpha-opic%20Toolbox%20User%20Guide.pdf |doi=10.25039/S026.2018.UG |quote=This User Guide relates to the &alpha;-opic Toolbox v1.049a, published by CIE Division 6. The Toolbox (DOI 10.25039/S026.2018.TB) and User Guide (DOI 10.25039/S026.2018.UG) are maintained under CIE Division Reportership (DR) 6-45.|title=User Guide to the &alpha;-opic Toolbox for implementing CIE S 026|date=2020 |last1=Cie }}</ref>