Colour Metrics - White Light
White light can not always be described as simply “white light”. For example, there is a clear distinction between the warm white light from an incandescent bulb in a domestic home, and the cold stark white light from a fluorescent bulb in a hospital operating theatre.
The CIE (Commision Internationale de l’Eclairage) has developed certain metrics to allow characterisation of white light (and colour). Colour matching functions, approximating the sensitivity of the eye to red, green, and blue, produced the 1931 Chromaticity Diagram. This diagram gives white light an associated set of chromaticity co-ordinates (x, y) that reflect its perceived colour and colour temperature. This is the foundation of the colour binning structures used by white LED manufacturers. The outer boundary of the diagram, or spectrum locus, defines the region for monochromatic light at a particular wavelength.
