The validity of a colour difference approach for evaluating the image permanence of photographic colour prints was determined by comparing its performance with that of optical density analysis, which has been conventionally used in this field. Criteria for determining the endpoints of photographic images are also proposed in this study. Light-fading tests were conducted for 20 consumer photographic and production prints, which were produced using dye-based inkjet, pigment-based inkjet, silver halide, electrophotography and D2T2 systems. The lives of these prints were evaluated on the basis of both optical density and colour difference data. Furthermore, the faded images were visually assessed by professional observers. It was confirmed that the colour difference approach produced results that correlated well with those of the visual assessment and that it was an effective measure for evaluating the image permanence of photographic prints. The results also indicated that the colour difference between faded and fresh images, 'ΔE76 = 10' or 'ΔE00 = 5', was appropriate criteria for determining the endpoints of photographic images.
Yoshi Shibahara, Evert Groen, Nobuhiko Uchino, "Evaluation of the Image Permanence of Digital Colour Photographic Prints Based on Colour Difference" in Proc. IS&T Int'l Conf. on Digital Printing Technologies and Digital Fabrication (NIP31), 2015, pp 135 - 139, https://doi.org/10.2352/ISSN.2169-4451.2015.31.1.art00030_1