LED colour point
The colour point (also chromaticity) of a light source is usually represented in the CIE standard colour system 1931. Each self-illuminating light source can be unambiguously specified by the x- and y coordinates. The wavelengths visible to the human eye are plotted on the curved outer contour, or spectral locus. The lower limit is the purple line, which is the limit of visible light to invisible UV and IR radiation. The white light area in the centre of the diagram is marked by the black body line (BBL). All of the colour points on the BBL are pure white and result from a mixture of a variety of visible wavelengths. The colour points on the BBL are differentiated by the mixing ratio of the wavelengths. If predominantly red wavelengths are present, this is referred to as warm white light. Cold white light, on the other hand, has a predominance of blue wavelengths.
On the BBL, the colour points of the colour temperatures are positioned from approximately 1000 K (Kelvin) to approximately 40,000 K. Light sources are referred to as warm white at ≤ 3500 K, neutral white at 3500 K to 5000 K, and cold white light at > 5000 K. If the colour point of a white light source is not on the BBL, this is due to an excess of a colour wavelength. Depending on the colour, this is referred to as yellow, green, blue or pink tinted. The BBL is cut by the CCT (Correlated Colour Temperature) lines. These lines are formed from colour points of the same colour temperature, regardless of whether they are pure white, or tinted yellow or pink.