Testing Canon135L lens with AF extension tubes

syamastro posted a photo:

First test with my new cheap (from China) macro extension tubes with electric
wiring (allows AF and aperture control of the lens) with my Canon 135mm f2L
lens. The magnification of such a combo is 1.1:1. I used a flash (Canon 580
EX) attached to the camera with a DIY softbox. The aperture was f/16 -
probably too small, as diffraction effects were pretty obvious. The shot was
slightly cropped.