Sorry but I wasn't using the Pentax 1.7x AF converter on an AF lens. I just wish to say the converter is pretty bad optically. That is to say I won't use it on anything, AF or manual...
Perhaps you got a bad one - I've used the 1.7x and A*400 for most of my birding in the last couple of years, and the combo works great. On that lens, the 1.7x AF and the 1.4x A-L are virtually equivalent in performance - both are excellent.
A sample shot with the 1.7x :
http://www.markcassino.com/galleries/birds/0308b18.htm
On a full res scan the detail in the feathers is outstanding.
- MCC ----- Mark Cassino Kalamazoo, MI -----
Photography:
http://www.markcassino.com
