Ozaphan films: preliminary study on color analysis and digitization

Ozaphan is a historical type of motion picture film made of cellophane, which exploits a silverless printing technique called diazotype used only for positive prints. These films were produced in the late 1920s up to the 1950s, initially in France and later in Germany, catering mainly to the home cinema market and therefore being printed primarily on small gauges. Ozaphan films were intended to be black-and-white films but ended up with a characteristic yellow hue due to the phloroglucinol used in the photosensitive solution.Although Ozaphan films were produced in relatively small quantities, we still find these prints in many European film archives today. Nonetheless, not much research has been carried out on this film material's conservation and physical characteristics.This study aims to document Ozaphan’s color characteristics by presenting an in-depth color analysis of the latter, achieved mainly through spectrophotometric instrumentation. The measurements have been carried out both on the light parts as well as on the dark parts of the frames to try and identify the exact hues of the yellow tendency of the prints. These types of colorimetric measurements can be firstly a relevant record of the current state of preservation of the films and secondly a reference during digitization and future digital restorations.Digitization certainly is a valuable tool for preserving and distributing audiovisual heritage. However, it involves modifying or excessively approximating the representation of some intrinsic characteristics of the materials, like colors. Thus, the second step in this study has been the attempt to apply the measurements of the transmittance color values both during scanning and the subsequent color correction phase to digitally preserve the actual hues of the Ozaphan films.Though still experimental, the results can be a useful hint for the approach to scanning, and the colorimetric measurements are a reference for further studies of Ozaphan films.