Subjective and objective measures of colour hard copy images

Abstract

The present report concerns an experimental comparison between subjective and objective measures of standard colour test samples chosen to represent hard copy images. Three attributes of colour, hue, chroma and lightness were examined. The study investigates the correlation between the subjective and colorimetric evaluation, in CIELAB uniform colour space. Subjective and objective tests are reported for tests using Pantone colour swatches, corresponding to the basic hues of an IT-8 chart, and additional swatches chosen to cover a wide gamut. Psychophysical investigations, using white, grey and black backgrounds, were carried out with a panel of 11 observers and are compared with the results of colorimetric evaluation. Experimental results show linear relations, with very good correlation between objective and subjective results, for hue determination, but less good correlation for lightness and chroma. The effects of the luminance of neutral backgrounds, on subjective judgements, are also shown. The evaluation of results is extended to a consideration of CIECAM 2002 colour appearance variables, expected to relate to observers' assessments of the test colours seen against neutral backgrounds differing in luminance.

Keywords:

• PANTONE COLOUR SETS
• VISUAL COLOUR SCALING
• CIELAB COLOUR SPACE
• COLOUR APPEARANCE MODEL