Originally posted by netuser How does it work with sdm lenses ? It's like the 1.4 tamron ?
I'm not sure I understand your question. But I'll try.
I'm not sure how to describe this. As I understand it, it works by optically changing the register distanse. In other words, if the lens is out of focus, it compensates for this, within a limit. You need to "halfset" the lens. Then the TC does the rest of the job for you.
It works fine, except it does not report correct focal length to the camera. Usually focus is accurate, and much faster than most AF lenses.
Optically it is good for a TC, but I'm not a big fan, I often prefer to crop.