Well, I received my Kenko tubes a few days ago, and now I need some guidance in figuring out how to make the best use of them. I got the 3-tube set (12, 20 and 36mm) in hopes of using them as a cheap alternative to buying a dedicated macro lens. My main interest is in shooting flowers, preferably handheld. 3 tubes plus multiple lenses = lots of choices. So, based upon my lens line-up (see my sig below), which length tube would be best to use with which lens, and why? I know that I need to experiment with different combinations, but I'm hoping that the experienced Kenko tube users here will help me flatten the learning curve, by reducing the number of permutations to try. Thanks!