The subject of image assessment and specification is of canonical importance to those involved in the research, development, and utilization of imaging systems. The quantitative assessment of something as subjective as the value of an image is essential in quantifying and communicating the needs and results of an imaging system or its components. In spite of the urgent need and the vigorous effort of the technologist responding to this need, no universally accepted standards for the measurement of image quality are available. The utilization of Fourier methods in image assessment and specification problems is currently in vogue because of their dexterity in fulfilling at least two necessary conditions as a measure of image quality. First, the Fourier methods provide a quantitative measure of image quality which reasonably correlates with the subjective effectiveness of an imaging system, and second, the analysis and performance prediction of a cascaded imaging system from a knowledge of the performance of its individual components are facilitated.