Minimizing granularity is a key goal when designing digital photo printing media and hardware. A granularity metric that correlates well with visually perceived graininess requires measuring image noise over the entire range of image densities. We present a flatbed scanner based method of measuring granularity on a continuous (stepless) density wedge. Only one scan is necessary to provide granularity as a function of density, and hence visually weighted graininess. Digital filtering separates the spatial micro-density variation from the continuous change of density before calculating noise power spectra as a function of density with high density resolution, higher than obtainable from a step wedge target. The method has been developed into an efficient and powerful tool for characterizing and optimizing thermal print media and hardware.
Dirk W. Hertel, Bror O. Hultgren, "Scanner-based Granularity Measurement on a Continuous Density Wedge" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP18), 2002, pp 189 - 194, https://doi.org/10.2352/ISSN.2169-4451.2002.18.1.art00046_1