The pixel structure associated with digital printing systems imposes image quality limitations on the print, and these may be a serious impediment to achieving the highest quality levels associated with analog prints. Print resolution or sharpness is a leading component of image overall quality, and will clearly be directly influenced by the pixel dimensions. A metric for image sharpness is proposed which combines the pixel dimensions and the perceptual response of the visual system in an appropriate Fourier-based manner. The resulting digital sharpness scale (DSS) is thus similar in approach to the digital noise scale (DNS) previously described by the author. The digital sharpness scale enables print requirements to be established for digital photography in terms of format, total number of pixels and degree of enlargement, in order to achieve the comparative sharpness levels established for conventional analog photographic processes.
Rodney Shaw, "Factors Influencing the Sharpness of Digital Prints" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP15), 1999, pp 446 - 449, https://doi.org/10.2352/ISSN.2169-4451.1999.15.1.art00019_2