CIE whiteness and tint: Possible improvements

To introduce some measure of standardization in the face of the endless variety of whiteness formulae being used, the 'Commission internationale de l'eclairage' proposed in 1986 a whiteness and a tint formula for practical trials. The formulae in question were simplified derivatives of those used in the Ganz-Griesser method. The difference is that the CIE proposes fixed formula parameters and recommends the formulae only for relative assessments valid just for measurements with a single instrument at a given time and without reference to a white scale. Assessment with the formulae is appreciably improved if the sample illumination is stabilized and fitted as close as possible to a desired standard illuminant, as with the Gaertner-Griesser UV adjustment device. It also greatly improves the matching of different measuring instruments, though only for whiteness. The tint values can only be satisfactorily matched by instrument-specific calculation of the formula parameters as practised in the Ganz-Griesser method. The CIE method can be upgraded and markedly extended in scope by incorporating components of this new procedure, as suggested in the present paper. This takes account of the growing need to achieve a close match even between the results obtained with instruments of different designs.