Wednesday, December 22, 2004, 3:21:39 PM, John wrote:
JW> I'm considering purchasing a Kenko 1.5x TC to go with the Sigma 135-400 APO
JW> zoom I recently won on eBay. I've read various (conflicting) comments on
JW> performance and wondered if anyone had any experience with this particular
TC.
JW> My main concerns are optical performance and retaining AF with the Sigma
zoom.
JW> The Sigma 1.4x EX TC will not work with this lens due to the position of the
JW> lens rear element. Any advice, comments or alternative recommendations would
JW> be much appreciated.
Hi John,
I am not familiar with your lens. Sorry if I am saying the obvious,
but are you aware that the 1.5x will make your lens f/8 at the long
end? Autofocus is generally good only up to 5.6, and depending on
particular camera, you may get very poor or even none AF at f/8, or
it might focus only in very bright light (full sun).
Good light!
fra
