This characterization addresses image systems that combine image gathering and display with digital processing for signal coding and image restoration. The alterations may vary widely, according to need or taste. Normally, however, the goal is to produce images that are sharp and clear, without perceptually annoying or misleading distortions, and to do so for a wide variety of scenes at the lowest cost in data transmission and storage. This goal, to consistently and economically produce the best possible images, leads the proper characterization of image systems into the realm of communication theory.
Communication theory is concerned explicitly with the transmission and processing of signals.
Modern formulations of this theory are based largely on the classical works that Shannon 1 and Wiener 2 published over 50 years ago, in the late 1940's. 3 Fellgett and Linfoot 4,5 were the first, in 1955, to extend these concepts of communication theory to the characterization of image systems. Their extension addressed photographic image systems in which an objective lens forms a continuous image of the captured radiance field directly on film. The formation of this image is constrained by the blurring due to the objective lens and by the granularity of the film, similarly as the transmission of a signal in a communication channel is constrained by bandwidth and noise. Digital image systems, however, are more complex.