Originally Posted by
DanK
Back to the original topic--it's been years since I read about the algorithms used in focus stacking, but if I recall correctly, they don't increase detail in any plane already in focus. Rather, they attempt to pick out the in-focus areas from each image in the stack (the various algorithms do this differently) and then composite them. If I am right, the appearance of additional detail is just a result of having so much of the final image in focus.
In much the same way, I played around years ago doing macro with apertures that clearly cause diffraction--e.g., a nominal f-stop of 22 (an effective f-stop much higher) on an APS-C camera. Doing this with a deep subject, e.g., a flower that is large front-to-back, creates an image that strikes people as sharp, even though the focal plane is less sharp than it would be at a smaller aperture, because so much more of the image as a whole is roughly in focus.
If I have this (the first part) wrong, please correct me.