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.