The illuminance of standard daylight, D65, that would produce the same stimulation of melanopsin-containing ipRGCs as the actual light at the eye. It is calculated from the spectrum and measured vertically at eye level. Consensus recommendations call for at least 250 lux melanopic EDI during the day, under 10 in the evening and under 1 during sleep, and building standards use similar metrics for circadian lighting credits.
We've got 400 photopic lux at the desk but only 180 melanopic EDI at the eye, so the 3000 K option misses the daytime target.
Circadian metrics are measured at the eye, in the vertical plane, so a design that meets them on desks can still fall short where it counts.
Also heard as
- mEDI
- melanopic equivalent daylight illuminance
Related terms
ipRGC
Intrinsically photosensitive retinal ganglion cells: eye cells that sense light for the body clock rather than for vision.
SPD
Spectral Power Distribution: a graph of how much power a light source emits at each wavelength.
Tunable white
LED lighting whose color temperature can be adjusted, typically between warm and cool whites, by mixing LED channels.
CCT
Correlated Color Temperature: the warm-to-cool appearance of white light, stated in kelvin.