As a blackbody heats from about 1000 K to infinity, its color moves from deep red through orange, white and into pale blue; plotted on a chromaticity diagram this path is the Planckian locus. White light sources are described by how close they sit to it: CCT names the nearest point on the curve and Duv gives the distance from it. Incandescent lamps fall almost exactly on it; LEDs often sit slightly above or below it.
Tunable fixture tracks the Planckian locus from 2700 to 5000, but at 4000 it drifts a bit above the line.
Also heard as
- blackbody locus
- blackbody curve
- BBL
Related terms
CCT
Correlated Color Temperature: the warm-to-cool appearance of white light, stated in kelvin.
Duv
How far a white light's color sits above or below the blackbody line, giving it a green or pink tint.
Chromaticity diagram
The horseshoe-shaped chart that maps every visible color by its chromaticity coordinates.
Tunable white
LED lighting whose color temperature can be adjusted, typically between warm and cool whites, by mixing LED channels.