Equal-value gray scales devised by cartographers and psychologists vary largely because of differing experimental designs and processes governing conversion of surface reflectances to inked-area percentages. Reflectance measurements for inked gray tones of a given area demonstrate a non-linear relationship. Mathematical models of printed paper's surface reflectance predict non-linearity of the same degree as that measured. This measured non-linearity is used to convert the Munsell and Stevens equal-value scales to inked-area percentages. Comparison of scales devised by cartographers over the years show that all except the Williams scale are similar to the Munsell value scale.
No takes yet. Share an insight, caveat, or question.
Jon A. Kimerling (1985) studied this question.