Imaging Methods and Quantitative Measurements for the Characterization of Digitally Printed Materials

Over the last five years, researchers at the Image Permanence Institute at the Rochester Institute of Technology have been developing an imaging strategy and a set of quantitative measurements that can be used to characterize modern digital print materials (both images and documents). While the goal of the project has ultimately been to enable personnel in cultural heritage institutions to identify their collection materials, the approaches should also be helpful to the field of forensic document examination. The imaging methods include varying the angle of lighting as well as the level of magnification. Structures such as surface gloss and texture as well as dot morphology and pattern can be assessed and compared to known print types. Additional, unique traits such as colorant bronzing, differential gloss, anti-block layers, etc. can also be used to narrow down the identification of particular print examples. This paper will describe the main approaches used for both imaging and quantitative measurement of print samples along with descriptions of where support tools can be found online.