My teleconverter sucks!

It's a Quantaray 2x. I can't use AF with any of my zoom lenses out to max, and the nifty is just a blur (not to mention useless as i have three lenses the cover 100mm). I'd hate to say i bought a piece of crap, but until I can get some quality shots using MF, this thing is USELESS!!!!!!!!!

Quantaray ALWAYS makes Junk. Thank RITZ and WOLF Camera for the turd.

Well, first of all, you will always lose AF on a non-1 series body with a 2x TC on any lens that is not at least f/2.8 or faster. That's not a problem with the teleconverter, that's a limitation of your camera. Non 1 series cameras can only use AF on lenses f/5.6 or faster...and if your zoom is, say, an f/4 to f/5.6 aperture zoom, it'll be f/11 at the long end with a 2x...not even my 1Ds Mark II will autofocus at a max aperture of f/11.

Teleconverters are not made for lenses shorter than about 100mm, so it's no wonder the 50 looks like crap with it. That said, a 2x TC is also going to have pretty severe image degradation on all but the very best lenses...there is no free lunch. Now, I don't know what TC the Quantaray is a clone of, but it is likely a Kenko or Tamron clone...if it's a clone of the Pro Kenko, it's actually a pretty good TC...but you won't be able to see it unless you try it on a piece of very good glass, such as the 300 f/2.8 or 200 f/2.

Stick to a 1.4x TC for most lenses, and I'd frankly avoid a TC altogether unless you are using very good lenses, as the image degradation will be too great. The 70-200Ls (all of them) take a 1.4x TC pretty well, but that's a starting point. If you've got a cheap consumer zoom, forget using a TC.

nureality wrote in post #8242232
Quantaray ALWAYS makes Junk. Thank RITZ and WOLF Camera for the turd.

Quantaray is almost always a rebadged Tamron or Sigma, so that's a pretty interesting statement...true, the lenses they rebadge are usually the bad ones, but not always.

The Quantaray TC's are BOWERs. And not even the GOOD ones.

But JMAN is correct, the problems of the AF are not a function of the TC but of your camera body.

nureality wrote in post #8242296
The Quantaray TC's are BOWERs. And not even the GOOD ones.

In that case, the TC does likely suck...but don't expect a big improvement even with the Kenko Pro with cheap lenses with a 2x. (I'd say the same about the Canon, but you can't use the Canon on cheap lenses...it won't fit!)

You could always do what I did to my crapola 2X TC - pull the lens out & use the remaining body as an extension tube...

I have one of the BOWER 2X TC's... badged as "Digital Innovations", basically a SAKAR hunk of crapo...

But its not terrible when used on decent glass, not great mind you, but for $90 it gets the job done - to a degree. My 70-200 f/4L IS with the 2x TC gets decent shots, it will hunt for AF, but it works some of the time since it doesn't report its presence to the body, so the body thinks its still @ f/4. And when it hunts, I just use the FTM of the lens to adjust it. Eventually, I'll replace it with a real TC, but for now I have better things to do.

I'll take the camera any day. Been thinking about a 40D, but I don't use the XT enough to warrant anything that expensive.

Maybe if I get another one cheap. It does focus with the 100-300 and the 70-300. just not when it gets near max zoom. Even though it's four years old now, it still cost too much to do that right now.

I'm actually pretty happy: 1) I'm not the alone with this problem. 2) I learned something about my camera! 3) I have some more ideas for maybe when I can tinker with my stuff without feeling guilty. 4) It's still in the bag; out of sight, out of mind. I don't even care right now!

Thanks to all