I would like to buy a sigma 135-400 mm lens with a converter (kenko 2 mc). Does someone have experiences with this lens or with this converter? Or with this lens with a other kind of converter? Thanks a lot. Arie

-- ariebokkerijder (confrater22@hotmail.com), April 25, 2002

Answers

Nope. No experience with this lens. Just hearsay. But I have tried teleconverters with other lenses & found a few things.

Any teleconverter magnifies any softness of the original lens. And that's if the teleconverter doesn't add any optical degradation of it's own, and they all do. 1.4x TCs magnify these flaws less than 2x TCs. Some are better than others. More money usually buys better TCs. A good TC on a very sharp lens often works very well. If one or the other is not very, very good, the image suffers considerably.

The Sigma 135-400 isn't a bad lens, but is not noted for being very sharp. So adding a TC to the mix will provide definite image degradation.

Then there is the question of auto focus. The Sigma 135-400 is f/5.6 on the long end. Adding a 2x TC will make this an 800mm f/11 lens. No Canon EOS camera will autofocus with it. If you use a 1.4x TC the lens will be a 560mm f/8 lens. An EOS 3 or 1V will focus with it with some limitations in AF points.

As long as you don't use a Canon brand TC the camera will not know it has a smaller than advertised aperture so the camera will try to AF. My experience is, most EOS cameras will be able to AF with an f/8 combination, providing there is enough light and contrast, but it will often hunt back and forth before it finds focus & often does not.

Most EOS cameras are not designed for good manual focusing.

-- Jim Strutz (j.strutz@gci.net), April 25, 2002.

I have a Sigma 170-500mm and Kenko 1.5 MC. I believe this combination would bring better results than yours because the teleconverter's magnification is smaller.

BUT I strongly disappointed at the results. Every shot has strong fall off at the corners, something like vignetting by wrong hood system. So I do not recommend to buy Kenko 2 MC teleconverter.

If you need 800mm or more focal length, you'd better consider Sigma 50-500mm EX and Sigma x2 EX teleconverter. 50-500 lens is expensive, but Sigma EX teleconverter can not put on 135-400 nor 170-500 lens.

Ken

-- Ken Itoh (KEN@clara.oc-to.net), May 10, 2002.