Autofocus with 1.4x or 2.0x

[PicTheShot]

Can anyone tell me if using a multiplier (either 1.4x or 2.0x) with a canon 70-200 L IS 2.8 and a 10D will have any effect on the speed and accuracy of the autofucus.

[Scottes]

Both will have an effect comparable to the light loss. My 70-200 f/2.8 with the 1.4 TC doesn't "snap" into focus like it does without the 1.4. But it's still certainly usable. I'd say that it's still a little faster than my 100-400 L, which is f/5.6 at 400 (my normal working length).