An optimisation study of colour measurements on digitised slides of painted works of art

This paper deals with the problem of the colorimetric fidelity of digitised colour slides of painted works of art. A six-matrix conversion model was d erived that permitted the transformation of any RGB device-dependent measur ement on digitised colour slides to XYZ CIE 1931 device-independent values. The model was calibrated against a reference colour chart. Eighty-one unif ormly-painted colour samples were photographed together with a painting on a 4 x 5 inch colour slide that was digitised using a high resolution scanne r. A 3 x 3 transformation matrix, of the corrected R, G and B values and th e respective X, Y and Z tristimulus values provided by spectrophotometry, w as calculated. The calculated matrix was then applied to a 13th century Byz antine fresco, captured on the same digitised slide, to transform the RGB m easurements to XYZ CIE 1931 device-independent values which were then conve rted into the L*a*b* CIE 1976 colorimetric system.