Threshold Metric Chroma of Images for Chromatic Perception

Abstract

Having a final goal to reveal psychological effect of saturation increase in digital images, BCACI, Border Chroma between Achromatic and Chromatic Impression, was investigated for normal and shuffled-mosaic natural images as the first approach. Observers were asked to respond total color impression by choosing one color name among 14 color names including basic categorical colors. BCACI was obtained by the effective metric chroma Cab * where 50% of responses were achromatic color names. Results of normal images indicate that when the metric chroma Cab * exceeds 7, observer's perception of the whole image turns from achromatic to chromatic, except "pink" and "purple" images. BCACI of shuffled-mosaic images is significantly lower than that of normal images, suggesting the effect of the meaning of contents on color impression.