COLORIMETRIC CHARACTERIZATION OF A DESK-TOP DRUM SCANNER USING A SPECTRAL MODEL

A desktop drum scanner was colorimetrically characterized to an averag e CIELAB error of less than unity for Kodak Ektachrome transparencies and Ektacolor paper, and Fuji Photo Film Fujichrome transparencies and Fujicolor paper. Independent verification on spectrally similar mater ials yielded an average Delta E(ab) error of less than 2.1. The image formation of each medium was first modeled using either Beer-Bouguer or Kubelka-Munk theories and eigenvector analysis. Scanner digital val ues were then empirically related to dye concentrations using polynomi al step-wise multiple-linear regression. These empirical matrices were required because the scanner's system spectral responsivities had exc essively wide bandwidths. From these estimated dye concentrations, eit her a spectral transmittance or spectral reflectance factor was calcul ated from an a priori spectral analysis of each medium. The spectral e stimates can be used to calculate tristimulus values for any illuminan t and observer of interest. The methods used in this research are base d on historical methods commonly used in photographic science.