How does it work??

[Stuart444]

I've been discussing the use of stacking software with a friend, and to make any progress with what we were discussing * I need to have an idea of how the software works. The top level explanation, something like "is takes the sharp areas from each stacked image and assembles them into a single sharp composite image", is too vague and simple. Is there a description in more detail, including what weighted average, depth map and pyramid methods actually do?

* What we were discussing was whether or not using more images in the stack than are needed (say by using Helicon Remote and following its guidance on how many images are needed) causes a degradation in the result. I've always thought that it would cause a quality loss because the camera is not absolutely rigid under most circumstances so having more images to align by the software than are necessary to meet focus bracket requirements might lead to a loss in final quality. Maybe this is nonsense - please tell me if it is! But I'd still like to know what the software is doing to come up with its brilliant results.