Correlated Color Temperature (CCT)

CCT describes the color appearance of white light, in kelvin, by comparison to an ideal blackbody radiator. Lower values are warmer (2700–3000 K, amber-white), middle values neutral (4000 K), higher values cooler (5000–6500 K, blue-white daylight). Industrial practice: 4000 K for most factory and warehouse interiors, 5000–6500 K where alertness and contrast matter (inspection, security), 2700–3000 K for residential streets and ecologically sensitive areas since warmer light scatters less and attracts fewer insects. CCT does not describe color accuracy — that is CRI — and two fixtures at the same nominal CCT can differ visibly, which chromaticity tolerance (SDCM) controls.