Image Gradation, Graininess and Sharpness in Television and Motion-Picture Systems: Part IV, A & B: Image Analysis in Photographic and Television Systems (Definition and Sharpness)

The theory of image formation and analysis is formulated in Section A as an “aperture theory” applied to optical and electrical image-forming systems. It is shown that the properties and combination of “apertures” (point-images) can be described in the space domain by transmittance functions and in the frequency domain by their Fourier spectra (sine-wave response). The mathematical formulation demonstrates that the basic operation of image formation and analysis is a successive integration of the products of two functions, letting one function “scan” the other function, mathematically termed “convolution.” The equivalent passband N6of an aperture or system emerges again as a significant and convenient parameter for specifying their characteristics by a single number.