> 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).
Thanks for the comment, I think I'll just have to take a chance, apparently this particular TC works well with the 170-500 APO zoom retaining AF, a similar design but apertures are slower than the 135-400. I'm on a cheap a cheerful route to getting a lens with a 600mm FL :) It's a bit hit and miss with TC's, sometime you get a workable combo and sometimes not IMHO. John ---------- Original Message ----------- From: Frantisek <[EMAIL PROTECTED]> To: John Whittingham <[email protected]> Sent: Wed, 22 Dec 2004 21:52:18 +0100 Subject: Re: KENKO (Teleplus) 1.5x TELECONVERTER SHQ 4 ELEMENT > 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 ------- End of Original Message -------
