The current ANSI standard method for evaluating the image stability of photographic prints (ANSI IT9.9-1996) calls for the use of densitometry in order to determine the extent of light-induced fade and to provide an estimate of print-life under real-world conditions. End-of-life criteria based on densitometry can involve monitoring simultaneously as many as 24 different end-points (excluding changes to Dmin). Conceivably, end-of-life criteria based on colorimetric measures such as ΔE or ΔC could reduce the number of end-points from 24 to as few as 7—one criterion for each primary (cyan, magenta, yellow), secondary (blue, green, red), and neutral (gray/black) test patch. In the context of evaluating inkjet photographic prints based on hundreds of different combinations of various manufacturers' inks and receivers, we have been following the kinetics of dye-fade by both Status A densitometry and CIELAB colorimetry. In this report, we will begin to explore the empirical correlation between densitometric and colorimetric measures of color change.
Douglas E. Bugner, Cory McWilliams, "Correlating Changes in Densitometry and Colorimetry in the Context of the Light-Induced Fade of Inkjet Photographic Prints" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP18), 2002, pp 753 - 756, https://doi.org/10.2352/ISSN.2169-4451.2002.18.1.art00082_2