The Canon TCs aren't compatible, of course, so I need to choose among the third-party units. I noticed some of them say that they're for lenses that are 90mm or greater, what happens if I use one of those (on a 350d) with the 85mm?
The Kenko Pro 300 3x is tempting, but I'd rather avoid attention-grabbing white.

dosbears wrote:
what happens if I use one of those (on a 350d) with the 85mm?


You will lose image quality.

But technically, Tamrons and Kenkos should work.

Thanks, I know that technically I'll lose some quality. I was wondering why they say "90mm or greater"? If it's a vignetting issue, would it still matter on a 1.6 crop like the 350d?

I have a Kenko Pro 1.4x, and it works fine with the 85. Unfortunately, beyond making sure it works, I have not taken any shots with the combo.

Thanks. Is that the Kenko 1.4x Teleplus Pro 300 DG, for about $195?

I think that for the quality you will receive with a 3X TC, you might be better off buying a cheap 70-300 zoom. The price and quality will be about the same.

I might just have to buy one to test that aphorism. I already have a 100-300 zoom....

Technically, they may not work properly. Test before buying.

e.g. A Tamron 1.4 will not work on a Tamron 90mm macro.