Finally, the measured colour coordinates of the high-power LEDs are depicted in the CIE 1931 colour space chromaticity diagram
According to the definition, we calculate the normalized chromaticity coordinate x, y, z in the equation below, which can be pointed in the chromaticity diagram
Error ellipse (visual limits): The plotted limits of variation in visually indistinguishable color coordinate values that form an elliptical shape around a central color value when plotted in a chromaticity diagram
We chose the CIE L*u*v* space (and their corresponding chromaticity diagram
CIE u'v') because of the easy psychophysical comprehensibility of their dimensions (see Hunt, 1995).
There has been concern about possible color confusion among red, orange, and yellow sign colors, especially at nighttime, since the FHWA specifications for these three colors are relatively closely spaced in the International Commission on Illumination (Commission Internationale de l'Eclairage-CIE) chromaticity diagram
32 on the CIE (Commission Internationale de l'Eclairage) 1931 chromaticity diagram
Thresholds that define red-green (RG) and blue-yellow (BY) sensitivity, within the neutral isochromatic zone, are plotted as x, y chromaticity co-ordinates in the CIE chromaticity diagram
That's why the LRC recommends using two metrics: CRI, which measures how similar a light source renders colors compared to a reference illuminant, and the gamut area index (GAI), which evaluates the relative area enclosed by sample colors on a chromaticity diagram
when rendered by the source.
AN ILLUMINANT'S POSITION ON THE CHROMATICITY DIAGRAM
(Figure 1) after exposure correction were close to chromaticity diagram
of standard colour table in a blue field (for the blue the increased colour difference after the correction is result of too much reduction in brightness due to underexposure).
In terms of the chromaticity diagram
, such a decrease means a shift outwards from the "blue" (lower left) corner of the diagram.
Featuring Windows-compatible software that can display a CIE chromaticity diagram
on a laptop, this compact system performs color repeatability and brightness sampling with 5 nm to 10 nm resolution in less than one minute.