Differential gloss is the term used to describe the condition where areas of a printed image, especially adjacent areas, appear to reflect light in different ways giving these areas distinctly different gloss appearances. This phenomenon is quite common in dry toner electrophotographic imaging and some ink jet imaging technologies. Differential gloss, while well known, is difficult to quantify in a meaningful way. One of the tasks undertaken by international standards community was to develop an image quality scale for the visual attribute of differential gloss. In an attempt to do this, experimentation was conducted using prints of three scenes. The results of this experimentation showed that the rankings made by the observers were scene dependent, indicating that the single number provided by measuring gloss differences on a patch target would be insufficient to describe the differential gloss perceived in complex images. The experimentation described in this study was undertaken to examine the effect of scene content on the perceptibility of differential gloss. The results indicate that gloss differences are more perceptible when they are central to the scene, are separated by well-defined edges, and of a feature size greater than about 0.5 cm but less than about 10 cm. The experiment also provided evidence that the presence of a human face can increase the perceptibility of differential gloss.
Susan Farnand, "Effect of Scene Content on the Perceptibility of Differential Gloss" in Journal of Imaging Science and Technology, 2011, pp 30505-1 - 30505-13, https://doi.org/10.2352/J.ImagingSci.Technol.2011.55.3.030505