Research on a model for evaluating the perceived sharpness of black text in digital prints

Evaluating text quality quantitatively has been a longstanding desire in graphic arts industry. This study aims to establish a model to evaluate the perceived sharpness of black text in digital prints. First of all, a test diagram, with three kinds of office used fonts which are all sized 10.5 Pt, was designed. Five kinds of digital presses based on different imaging mechanism were used to output the test diagram on 16 different kinds of paper commonly used in market. From the eight attributes of line/text quality in ISO/IEC13660 standard, three attributes - contrast, edge raggedness and line width were extracted out to be the main index to describe the text sharpness. Furthermore, connecting them with the subjective evaluation, a model for predicting the perceived text sharpness was established. The result shows that the perceived text sharpness is highly correlated with the three attributes, among which contrast and line width exhibit positive correlation with perceived sharpness, while edge raggedness exhibits weaker negative correlation. Thus the perceived text sharpness can be predicted through a liner model.