Musings about Photography and the Science behind it
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The Modulation Transfer Function (MTF) of an imaging system represents its spatial frequency response, from which many metrics related to perceived sharpness are derived: MTF50, SQF, SQRI, CMT Acutance etc. In these pages we have used to good effect the slanted edge method to obtain accurate estimates of a system’s MTF curves in the past.[1]
In this article we will explore proposed methods to determine Texture MTF and/or estimate the Optical Transfer Function of the imaging system under test from a reference power-law Power Spectrum target. All three rely on variations of the ratio of captured to reference image in the frequency domain: straight Fourier Transforms; Power Spectral Density; and Cross Power Density. In so doing we will develop some intuitions about their strengths and weaknesses. (read more…)