Thanks Carlos It doesn't sound that bad, I expect some losses when using a TC even the Sigma 1.4 EX and my 300 f4 APO although it's hard to detect in that combo.
I'll give the AF a try with the MZ-3 and my backup ZX-5n when I get it, see how things work out :) John ---------- Original Message ----------- From: Carlos Royo <[EMAIL PROTECTED]> To: pentax-discuss@pdml.net Sent: Thu, 23 Dec 2004 13:26:29 +0100 Subject: Re: KENKO (Teleplus) 1.5x TELECONVERTER SHQ 4 ELEMENT > John Whittingham escribió: > > 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. > > > > I have got one of those converters. The instruction manual says that > the lens needs to be f:4 or faster to keep AF. In practice, AF works > also with an F* 300 mm. 4.5, in bright light conditions. But AF > isn't only lens dependent, it also varies from camera to camera. For > example, if I use the F* 300 mm. + 1.7x Pentax AF converter on my Z- > 1, AF doesn't work in any circumstances, but the same lens plus > teleconverter on the MZ-S autofocuses very well. > > On the optical side, the Kenko is OK, but don't expect it to be as > good as the Pentax 1.7x AF or Pentax 1.4-S. With the Kenko you'll > soon notice some loss of contrast (not much), when compared to the > original lens without the converter, and sharpness will also be > slightly reduced. > > Carlos ------- End of Original Message -------
