CRITICAL ASSESSMENT OF CHROMATIC INDEX IN ARCHAEOLOGICAL CERAMICS BY MUNSELL AND RGB: NOVEL CONTRIBUTION TO CHARACTERIZATION AND PROVENANCE STUDIES

Hundred twenty archaeological ceramics (potsherds, figurines, stirrup jars) as well as experimental briquettes made from local clays fired at different temperatures were examined for their color index chromatic scale. Color was measured on clean surfaces, clearly fine decoration layers, from the Late Mycenaean settlement at Kastrouli, Central Greece. The aim is to critically assess these quantitative attributions of a color index to ceramic surfaces which depends on several factors, such as the type of clay, firing regime, subjective evaluation, lighting conditions. Our endeavor and aim are to classify groups of similar color that may imply same firing conditions and clay sources. The color perception within a chromatic context is investigated and the effect of light on color appearance is assessed. Indeed, apparent subjective differences in Munsell color evaluation, the sensitivity of chosen surface area and photo shooting setting under different light conditions are observed. Initially the evaluation of different color components, e.g. R, G, B; Lab; HSB, were examined using stereoscopic images as well as a mini digital micro USB microscope and edit with image processing software. Finally, the 3D plots and statistical clustering of RGB as average integrated and separate values with associated standard deviation error produce groups of similar ceramics compared to the briquettes. Results were corroborated by cluster analysis of R, B, G of sherds and fired clays.