Technique for Analysis of Surface Topography of Photographic Prints by Spatial Analysis of First Surface Reflectance

Abstract

Visual examination of a large number of historic photographs indicates a significant variation in the surface texture in the paper on which the prints were made. This suggests that a thorough survey and quantification of surface texture would provide a useful tool for verifying the provenance of historic prints. The objective of the current project was to develop a digital imaging instrument and analytical protocol for capturing and evaluating the surface texture of papers beneath the gelatin/silver image of historic prints. The technique developed to accomplish this objective involves unique characteristics of the gelatin/silver print but is based on well known optical characteristics of materials. In particular, the behavior of first surface reflected light from the gelatin is distinguishable from the diffusely reflected light from the underlying paper, and analysis based on these properties has lead to a useful analytical tool for extracting an image of the paper surface texture and digitally eliminating the diffuse photographic image.