DIFFERENTIAL COLOR THRESHOLDS AND NEW RESULTS ON FAILURES OF CHROMATICITY AND LUMINANCE PREDICTION

The experimental determination of differential chromaticity thresholds from metameric matches show discrepancies in colorimetric prediction using the standard observers established by the CIE [Hita et al., J Op t Soc Am A 1986; 3 : 1203-09 ; Jimenez del Barco et al., J Optics 17, 1986 ; 247-54]. In this work we have determined whether the discrepanc ies of colorimetric prediction are contained in the differential color thresholds. To study the possibility of generalizing prior results to a wider range of experimental conditions we have carried out new expe riments determining the differential color thresholds of an achromatic stimulus from metameric matches, using direct vision and a foveal fie ld of 1.5-degrees. The results are expressed in terms of the color-mat ching functions of CIE-2-degrees standard observer, as well as those p roposed by 2-degrees-Stiles and Burch and Nayatani et al. The discussi on of the results is made taking into account different causes which m ay explain the failures of colorimetric prediction detected : rod intr usion, interactions of the responses of cones sensitive to short-wavel engths, errors and matching imprecision. Results show that the failure s of colorimetric prediction obtained under our experimental condition s exceed the color differential threshold. These discrepancies increas e with the relative difference of the S-cone excitation level for the matched stimuli.