Light source criteria for digitizing color films

The poor stability of film dyes and the decline of film photography require the development of digitization techniques designed to acquire the full amount of color information carried by photographic film. The spectral characteristics of the light source used during the image acquisition extremely influence the quality of the final digital reproduction of color films; this paper thoroughly discusses the criteria to be adopted to properly choose the light source. A method is described to infer the analytical densities of a color film from a set of measurements of the integral density; this provides the necessary spectroscopic information for the choice of the light source. The experimental part reports the analysis of two photographic samples from archival material: a Technicolor and an Agfacolor from the 1940s. The experiments highlighted the peculiar spectroscopic characteristics of the analyzed samples. The attention was drawn on the historical aesthetics of color film and the ethical issues related to its preservation.