Suppose I have a blurry image: a photo convolved with a gaussian blur kernel of unknown sigma. I would want to deconvolve the blurry image using several gaussian kernels (with different sigmas). Is there some metric function that measures "sharpness" of the deconvolved image? I could have a user look at a sequence of images and pick the most sharp one manually but I would like to have some automated way of doing this. Thus this question.
I imagine that such a sharpness function must exist because modern cameras have auto focus feature. Auto focus adjusts focal lens (is that the right term for it?) based on some sharpness value being a function of a (more of less) blurry image.
I also realize that there is such a thing as blind deconvolution which does not exactly need to know what the point spread function was exactly, but I do not want to get ahead of myself here. But of course, all ideas are welcomed.