I'm considering purchasing a Kenko 1.5x TC to go with the Sigma 135-400 APO zoom I recently won on eBay. I've read various (conflicting) comments on performance and wondered if anyone had any experience with this particular TC.
My main concerns are optical performance and retaining AF with the Sigma zoom. The Sigma 1.4x EX TC will not work with this lens due to the position of the lens rear element. Any advice, comments or alternative recommendations would be much appreciated. TIA John
