This is based directly on CIE XYZ (1931) and is another attempt to linearise the perceptibility of unit vector colour differences. Again, it is non-linear, and the conversions are still reversible. Colouring information is referred to the colour of the white point of the system, subscript n. The non-linear relationships for L* a* and b* are the same as for CIELUV and are intended to mimic the logarithmic response of the eye.
L*=116((Y/Yn)^(1/3)) - 16 for Y/Yn>0.008856
L*=903.3(Y/Yn) for Y/Yn<=0.008856
a*=500(f(X/Xn)-f(Y/Yn))
b*=200(f(Y/Yn)-f(Z/Zn))
where f(t)=t^(1/3) for t>0.008856
f(t)=7.787*t+16/116 for t<=0.008856
Again, L* scales from 0 to 100.
Again, there are polar parameters that more closely match the visual experience of colours.
C* = (a*^2 + b*^2)^ 0.5 hab = arctan(b*/a)Hue is an angle in four quadrants, and there is no saturation term in this system.