Details:
Summary:
The digital printing reproduction process analyzed in the paper is composed of the steps of image digitalization, digital processing, halftoning, digital printing, analog duplication and, as the last step, human cognition. The overall purpose of the process is to relay the density signal of original images to prints in such a way that the visual quality becomes maximized under existing constraints. The digital process has the dual character of a signal transfer and an information transfer process. An implication is that the quality in the process are also determined by the influences of factors of these two kinds. The signal transfer, defined by the tone and detail rendering, is studied by means of system theoretical concepts. These provide a useful framework for the expression of the signal transfer in the analog process steps in particular. The expressions for the prediction of the information transfer in the digital as well as in the analog steps. The unified approach makes it possible to compare digital and analog operations in the process. The digital process has the dual character of a signal transfer and an information transfer process. An implication is that the quality in the process are also determined by the influences of factors of these two kinds. The signal transfer, defined by the tone and detail rendering, is studied by means of system theoretical concepts. These provide a useful framework for the expression of the signal transfer in the analog process steps in particular. The expressions for the prediction of the information transfer in the digital as well as in the analog steps. The unified approach makes it possible to compare digital and analog operations in the process. The requirements to the objective image quality set by human cognition are discussed in terms of visual thresholds. The factors covered include the visual sensitivity to quantization steps and the visibility of digital halftone dot structures. In the paper, emphasis is given to the presentation of the methods, both computational and experimental, which have been developed using the principles referred to above. Results are reviewed with the aim of elucidating the question of the limiting factors of the quality in digital printing reproduction.