At right is a detail of the ant claws, which was taken with the Raynox
MicroExplorer. The Raynox is a set of close-up lenses available for
about $150. I mounted the 6X lens on a Canon 35-350L zoom lens (the
kit also comes with 12X and 24X lenses).
Here is the original ant claw picture. You can see that vignetting was severe at f/16. Fortunately, I could see this in the viewfinder to a large extent with the DOF preview and Adobe PhotoShop papers over a lot of photographic sins. Vignetting is the principal drawback of the MicroExplorer and it is apparently worse at small apertures.
A couple more example MicroExplorer shots (at left is an Ant robot detail; at right is a quarter on a $20 bill, full frame at f/8 (I think)). Note that vignetting is not as severe as it was at f/16 (above left).