Correlated Color Temperature, which labels a white light with the blackbody temperature, in kelvin, that comes nearest to it in color. Lower numbers look warmer: 2700 K resembles incandescent, 3000 K is common in hospitality and homes, 3500 to 4000 K is neutral and typical in offices, 5000 K and above looks cool and daylight-like. CCT only describes where a white sits along the warm-cool axis; Duv describes its green or pink tint.
Spec calls for 3000 K CCT throughout, but those cove strips came in at 3500, you can see the difference on the ceiling.
Warm means low kelvin. The physics runs opposite to everyday speech, so a client asking for warmer light wants a lower number.
Also heard as
- color temperature
- kelvin
Do not mix it up with
- CRI: CRI rates how accurately colors are rendered; CCT only describes how warm or cool the light itself looks.
Related terms
Duv
How far a white light's color sits above or below the blackbody line, giving it a green or pink tint.
Planckian locus
The line of whites on a chromaticity diagram that a perfect blackbody passes through as it heats up.
CRI
Color Rendering Index: a score up to 100 for how true surface colors look under a source compared with a reference light.
Tunable white
LED lighting whose color temperature can be adjusted, typically between warm and cool whites, by mixing LED channels.
Warm dim
LED dimming that also lowers color temperature as light level drops, imitating the glow of a dimmed incandescent lamp.