Applying Mixed Adaptation to Various Chromatic Adaptation Transformation (CAT) Models

In 1998, a Technical Committee 8-04 was formed in CIE/Division 8, “to investigate the state of adaptation of the visual system when comparing soft-copy images on selfluminous displays and hard copy images viewed under various ambient lighting conditions.” Several past studies indicated that applying mixed adaptation to the chromatic adaptation transformation improves the prediction of color appearance of CRT monitor viewed under mixed illumination. CIE/TC1-52 has been investigating the chromatic adaptation transforms. Most of the color appearance models in early 90’s used Hunt-Pointer-Esteves (HPE) transformation. In late 90’s, Luo et al.’s experimental results indicated that Bradford (BFD) transformation was superior, and BFD transformation was then adopted in CIECAM97s. Recently, Thornton suggested optimum RGB primaries are at 450-533-611nm. It was of great interest for the CIE/TC8-04 members to test other chromatic adaptation transformation in S-LMS mixed chromatic adaptation model, which originally uses HPE transformation. Above three color spaces were used in the visual experiments, along with XYZ and sRGB color spaces. Experimental results indicated that BFD transform performed best, slightly followed by HPE transformation, when applied to S-LMS. It was also tested if the incomplete adaptation process was needed in mixed adaptation. RLAB method, D-factor used in CIECAM97s, and complete adaptation, were compared in S-LMS. RLAB method and Dfactor resulted in much better score than complete adaptation, indicating that incomplete adaptation process is also important. According the results, revised model for the SLMS, which is fully compatible with the revised CIECAM97s model, is proposed.