Whiteness evaluation: A review and new proposals

This publication carries out an in-depth study of whiteness, various numerical evaluation methods that have been developed over the past 75 years, and review their application and deficiencies in the context of a new proposed Commission Internationale de l'Eclairage (CIE) whiteness formula. The publication first introduces the basic principle of whiteness evaluation from the work of Judd and Selling around 1950, then that of Ganz in the 1970s and finally that of the CIE from 1969 to 1986. The defects of the Judd and Selling formulas became apparent with the use of fluorescent whitening agents. The CIE linear formula cannot predict an optimum for the optical whitening process. Hyperbolic formulas published are much too complicated and are unable to predict correctly the best conditions for that optical whitening. We present a new formula derived from that of the CIE, much simpler than the hyperbolic formulas, and able to predict an optimal shade in the optical whitening process. The formula takes into account the limitations of the white domain; when the blue saturation becomes too great, or when a tint deviation toward green or toward red is too noticeable. The formula gives results identical to those of the CIE formula when the materials are far from commercial whiteness limits. In addition, the formula can be very easily adapted to the CIELAB system and so, gives promising results.