Sigma's recommendations are based on the space between the rear element of the lens and the front element of the TC. If you can, try it out before you buy. That way you'll know if it will fit. For example: my 1.4x and 2x Sigmas work (as indicated on sigma's site) with my sigma 300/4 Macro and also work (not listed) with my Pentax SMC-A 200/4. They do not work with my vivitar S1 105/2.5 macro because the vivtar's rear element hits the TC's front element.
Also, Sigma says that the camera will not AF with the 2x converter and 300/4, but it does... barely! I rarely ever use AF for the 1.4x either because you can almost feel the camera struggling to focus. Christian Skofteland [EMAIL PROTECTED] ----- Original Message ----- From: "Amita Guha" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, May 31, 2004 5:12 PM Subject: AF teleconverters > I tried taking the istD out birding this weekend and I found that it's > just too hard to focus manually at an effective 1200mm, so now I'm > looking for a solution. The first thing I want to get is an AF > teleconverter. I looked at B&H and there seems to be quite a range in > prices. Tamron's 1.4 is just $80, but Christian's Sigma EX 1.4 is $169, > and on the website it says it only works with certain lenses, none of > which I have (and I have a fair amount of Sigma glass). Tamron's 2x has > no such restrictions listed and it's $144. Do I have to be careful when > I buy an AF teleconverter or is this just a marketing ploy by Sigma? > > Thanks, > Amita >
