Originally Posted by vachss
Being the damn fool gear collector I am, I ended up with a 2xIII about 6 months ago ($350 Craigslist deal I couldn't pass up). Honestly though, it's sharp but not worth the hype. At least on my 500/4 I couldn't see any real difference between it and the 2xII. Maybe on one of the new mkII superteles the enhanced AF would make it worthwhile, but for ordinary mortals with older glass I'd give it a pass.
Great deal. From what I've read, the real reason to get a Series III TC is to match it with a Series II lens to gain faster AF over the Series II TC.
It's funny, but even with a 2X TC, you're likely to crop a little, so you're working with the center of the image, which is going to be sharp.