Because most degraded documents are created by people, the preferences individuals have in relation to degraded documents are quite important. Their preferences may determine whether or not the documents they created are appropriate for machines. The goal of this study was to find relationships between preference and several parameters of a scanner degradation model. It was found that the difference in binarization threshold and the difference in edge displacement caused by the degradation both had strong linear relationships to preference. The width of the point spread function did not show such a relationship. These relationships were counterintuitive because degraded characters with thicker stroke widths than the original were preferred to those that had stroke widths closer to the original character.
Hale, Chris and Barney Smith, Elisa H.. (2007). "Human Image Preference and Document Degradation Models". International Conference on Document Analysis and Recognition, 2007, 257-261. http://dx.doi.org/10.1109/ICDAR.2007.4378715