Colour Consistency

The Black Body Locus (BBL) is a curved line that runs through the CIE colour space diagram.

It represents a line along which the colours of a light are perceived to be white above it, and the light can appear greenish white below it. White light can appear pinkish white. 3000K for example sits on the BBL, if the colour shifts to the right a little the white light will appear warmer (a lower CCT Kelvin value), if the colours shifts to the left a little the white light will appear cooler (a higher CCT Kelvin value). Macadam ellipses are concentric rings often shown centred on a CCT on the BBL. The first ring closest to the centre represents the boundary within which the differences in colour between the centre and the limits are indistinguishable by the average human eye.

Each ellipse represents one step. The concept is extended and standardised as standard deviation colour matching (SDCM).  

Recognising that colour consistency is important light sources/luminaires offering a lower SDCM value represent products with a tighter tolerance on colour point. If the industry norm on initial colour consistency is 3 SDCM (3 step) then 2 SDCM (2 step) might be consider premium. Some light source manufacturers offer sources where the initial colour consistency can be stated as 1x2 SDCM, that is 1 step in up/down direction (limiting greenish/pinkish tint) and 2 step in the horizontal direction.

Stoane Lighting use light sources with initial colour consistency under 2 step. The COB based products we use often have 1 x 2 SDCM