A few shots of gold 20 franc coins

These coins are taken from an oblique angle using a technique called focus stacking, where images are taken at slightly different focus settings and then stitched together with a computation analysis process to identify the bits with the best focus from each source image.

Some years ago (quite a lot of years ago) I had the casual acquaintance of a mathematician who was doing some research on a similar field - using this type of analysis to stitch satellite images together.  We were discussing ways he might get hold of a machine, essentially a supercomputer by the standards of the day, on the cheap so he could run the process in a reasonable time.