This setup is outdated. It was working, but mounting a Dandelion chip in the small extension tube is much more comfortable. It might still be interesting for Canon users, since they can control the aperture electronically.
See an example shot here!
Mounting a lens reversely to get high magnification is a well known technique for macro photography. I did not want to dispense with the electronic link so I modded two extension tubes to ensure proper electronic connection. The process was more critical than expected, since there is surprisingly much mechanic in the tubes. Very thin wires were required (see detail) to make it fit.
My D90 can meter the exposure. Some flashs (like my Sigma) needs TTL metering to be driven beside maximum or minimal manual settings. With this setup I still have to correct the exposure and of course manual is still the mode I use, but ISO and flash power driven automatically is a great thing!
Of course the tubes can still be used regularly!
I've also added a 5W Cree LED as a macro light which helps significantly to find the focus spot. It
is powered by an external battery.
See comments for the complete setup or have a look at my macro equipment set for the evolution of my setups.
Of course I also have a set for the resulting macro images!
Thanks for the clicks, hackaday!