Quote:
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Originally Posted by dc2
I am not sure why your not sure for sure [why "sharpening" is an optical illusion that does not actually restore detail]
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Ideally, and if carried out perfectly, the mathematical process of
deconvolution would be able to undo the bad effects of camera/subject movement, lens aberrations, diffraction, and other effects that would degrade the image. In practice, the presence of noise, lack of exact knowledge of the exact deconvolution function, and the fact that deconvolution can involve division by zero or nearly zero all prevent the reversal from being carried out perfectly. Nevertheless, even an approximate reversal can improve the resolution of the image. Unsharp masking mimics in a crude way the result of deconvolving certain kinds of image degradation. For those familiar with electronics, the result is much like Q-peaking a circuit to improve its high frequency response.