While reading some reviews of Canon EF-S 10-22mm f/3.5-4.5 USM, I was a bit surprised to notice that the lens is supposed to be compatible with 12mm and 25mm extension tubes, and with those one should be able to get maximum magnifications better than 1:1.
An ultra-wide lens for macro work sounds like a fun alternative, but does it really work in practice at all?
Have people had any success with taking macro shots using ultra-wides and extension tubes? Do you have any working distance at all between the lens and your subject? What about lighting the subject, does it become near-impossible with the lens shadowing everything?