Originally posted by Pablom I thought there is a Kenko 1.5X AF TC available
I think the Kenko 1.5X AF TC is a rebadged Tamron 1.4X AF TC (I'm sure someone will correct me if I'm wrong).
I have a Tamron 1.4X AF TC. Many people post it as "support Pentax SDM."
For the DA* zoom lenses I tested (16-50, 50-135, 60-250), the TC's autofocus works at shorter focal lengths (but then there is no reason to use a TC with the zoom at the short end). When the zoom is at the long end, at shutter release half press, the autofocus keeps hunting back and forth as if it can't decide. If I remove the finger from the shutter release, then quickly half press again, there is a good chance the autofocus will lock.
In other words, it "kind of" works, but is too iffy for action shooting.