I just ordered a REALLY cheap set of extension tubes on eBay, and they arrived today. They were like $7, because there are no electrical contacts. That means manual focusing and to set the aperture, I get to mount the lens to the camera, set an aperture, press DoF preview, remove lens while holding DoF preview, mount tubes, mount lens... Anyway, my understanding of tubes is that the shorter the focal length, the closer the focusing distance. Obviously if I go too short, my focusing distance will be so far back that it's inside of the lens. So I have a 9mm, a 16mm, and a 30mm tube. Out of the selection of lenses in my signature, what do you think my best bet is? I'm shooting for absolute maximum magnification before lighting becomes really difficult due to working distance. Ideally I want to go quite a ways past 1:1. Has anyone found a really good combination of tubes and a lens that yields intensely close-up macro shots?