Saturation of spectral lights*

Spectral lights, while constant in purity, differ in saturation. Saturation-discrimination experiments have not always indicated this variation of saturation with wavelength. For example, several early investigators determined the size of the first just-noticeable step from the spectrum locus and found it to be approximately constant as a function of wavelength. When we performed this experiment we found saturation functions with minima near 570 nm; however, the ranges of the functions were more compressed than saturation-discrimination functions near white. The saturation-discrimination function results are compared with saturation functions determined by several other empirical and theoretical methods.