AF Speed with 2x Converter. (1 Viewer)

I just acquired a Kenko 300 pro 2x converter.
Went to try it out yesterday with a 500D, and 200mm f2.8L lens.

While image quality was ok, I found that the autofocus speed was painfully slow. The autofocus worked but was really too slow to be usable.
The combination is basicly a 400mm f5.6 lense so I was not expecting any focusing problems. I have successfully used a kenko 300 pro 1.4x with my 400mm f5.6L lens on the 500D and had acceptable autofocusing in good light.

I have been reading about people using a 2x on the 300mm f2.8L and on the 70-200mm f2.8L II and know that the focus speed is slower, but nobody has indicted that it was so slow as to be unusable.

So is it my lens camera combination, or is it the kenko converter vs the genuine canon

I use a Kenko pro 2x on a 300 f2.8 and no problems with autofocus at all, wouldn't even call it slow to focus. I'm using a 7d so possibly the 500d is the problem.

As john-henry says it could be your 500d.
Is a Canon 2x as similar as a Kenko?
The Canon 2x works fine on my 300/2.8, don't see a loss in auto focus speed.

I use a 2x (Canon mkII) with my 300/2.8 most of the time Jim and AF speed is pretty good. The trick is to use a focus limiter - without a limiter and when the subject is a fair bit out of focus the AF can go right out to infinity, back to MFD and then out again to acheive focus, if you use a focus limiter (I mostly use 6.4m - infinity) this does not happen and AF is snappy. I have not experience of you set-up thought.

I use an old kenko non reporting 2X converter with my Sigma 300f2.8. there is no focus limiter. However it is very fast and I compared it with my friends Canon 500. There was no perceptable difference in speed when transfering from a subject about 4m away to another 400m away. The lack of a focus limiter can cause hunting and can be a real bummer at times but in many situations this can be overcome by pre-setting to the approximate focus distance you anticipate you may require. If you are having serious problems then I can only suggest carefully cleaning all contact points. If that does not work try another lens and if that does not work see if you can try a different but same make and model of camera. In short, eliminate all possiblities.

Thanks everyone. Adjusted the focus limiter on the lens and it helps. The focus isn't as fast as I would like but it is useable.