richms: I got the non AF extensions first, but found I really needed the appature control to get enough depth of field, with it fully open it was hopeless and would only get a few mm in focus enough.
There is a very very fine line between enough DOF to see a whole ring, and getting your lights clear in the reflections.
I also ended up putting a white sport sock with a hole in the end over the lens to reduce the amount of black lens reflecting off the rings. Helped quite a bit but there is still some black visible.
Just a tip, if you don't have aperture control.
Attach lens normally, select desired aperture, press the DOF preview button on the camera, and take the lens off while button is still pressed. The aperture will be set on that lens and you can use the tubes with that smaller aperture. Just put the lens back on the camera normally to adjust/reset.