Collin Brendemuehl let his curiosity get the best of him when he asked:
I've seen "A"-class extension tubes. But does anyone make one with the AF mechanism coupled through? Or would it be better to take a little 1.4xTC and strip the optical guts out of it?
Kenko makes an AF tube for Pentax. I have one but I've found very little use for the AF capabilities. In my experience, AF can't handle the precise focusing requirements in macro work.
It might be useful when coupled with an AF telephoto when you want to get closer than the lens' minimum focusing distance. I don't have an AF tele to try it with (yet).
IMO, you'd be ruining a good TC for something you'd very rarely need. Tom Reese
