COLORIMETRIC PURITY DISCRIMINATION - DATA AND THEORY

Colorimetric purity, measured as the first step from white toward the spectrum has a V-shaped function. Purity discrimination is best near 4 00 nm, least at 570 nm and intermediate at mid-spectrum and long wavel engths. A much flatter function occurs when colorimetric purity is mea sured as the first step from the spectrum toward white. In this study, we applied the formulation of chromatic discrimination thresholds mea sured along the S-cone and M/L-cone axis to account for chromatic disc rimination in the equiluminant plane. The modeling results show that t he purity step from white has a 1.6 log unit calculated range, similar to the classical data. The purity step from the spectrum is much flat ter. The predicted range is dependent on the individual variance in ch romatic discrimination thresholds and the luminance level. We then use d psychophysical procedures to test the model's predictions. The resul ting purity discrimination functions were generally in agreement with the model. Our modeling indicates that discrepant data of colorimetric purity can be explained with the context of discrimination models.