Multispectral imaging system using 12 interference filters for mapping pigments

Abstract

Multispectral imaging systems are used in art examination in order to map pigments and binders as well as retouches. This work presents a simple system composed of a monochromatic CCD camera and a set of only 12 interference filters characterized by different bandwidths and spacing throughout the covered electromagnetic spectrum (400-805 nm). The reasoning supporting the selection of these specific filters is discussed, as well as the results obtained on a collection of 54 historical pigments and on a series of 18th century frescoes in Sicily. Generally, the filters set for similar systems are chosen equally spaced across the recorded spectrum. For this study the centre wavelength and the bandwidth of these filters have been chosen accordingly to the spectral features of historical pigments. This system allows only for a qualitative reconstruction of pigments reflectance spectra. It must be considered a valuable tool for segmenting the images of polychrome artworks and to identify areas of interest for further analytical examinations if more conclusive results are necessary.