Does Kenko make good tubes? I have the 70-210 f4, it technically does macro but at a 1:5 magnification and only at 210 - one of those 'barely a macro' macros. So, rather then spending the extra money to essentially get something I already have in another lens, just bringing a little closer, should I get extension tubes? So long as the AF remains in tact, there are no other problems?
Here is the link to the one I am looking at, but I am open to other ones that are better of course... - link