Polychromatic MTF-based Criteria for Evaluating Photographic Image Quality

Abstract

The validity of a series of criteria for evaluating image quality based on the modulus of the polychromatic optical transfer function (polychromatic MTF, or PMTF) of the image-forming instrument is studied. The criteria are based on the area determined by the coordinate axes and the curve of the one-dimensional PMTF (calculated for objects varying only in one direction: bar test, sinusoidal test, slit). Quality criteria based on the two-dimensional character of the actual PMTF function (the Fourier transform of the point-spread function) are also proposed; these are especially suitable for image evaluation in off-axis zones of the instrument. A series of guidelines is set out for commercial optical systems (existing camera lenses), operating with reversal colour film processed in such a way that S n S = 1.