Correlate for Lightness in Terms of CIE-Tristimulus Values Part II*

A triangulation technique was used to check the definition of lightness as applied in the previous paper. The results indicate that the procedure of defining lightness in terms of the luminous reflectance of neutral samples is satisfactory.The investigation has been further extended to show a systematic dependence of lightness index on background color. As might be expected, the lightness index of colors similar to the background is decreased and the lightness index of complementary colors is increased relative to the lightness index obtained using a black background. This effect is due to the change in chromatic adaptation of the eye.