Originally posted by 5teve Ok had a reply from Tamron (well the repairer)...
Japan have advised me the A001P and A09P where developed long before live view was implemented and may not focus efficiently when used in live view and have advised to manually focus the lens when using this function. Optically adjusting these lenses can improve resolution which we can do but this will affect focus shift and only Japan has the tool for adjusting the focus shift on the Pentax version lenses, please note though this will not improve live view operation.
So I either manually focus (kind of impossible if I'm using liveview to get over crowds) or just ignore live view on these lenses.
I don't understand this answer. Conceptually, CDAF is supposed to work the same as what we do with manual focus - turn ring to left until image goes from sharp to less sharp, turn ring to right until image goes from sharp to less sharp.... keep doing this process looking for point of maximal sharpness.