I just picked one of these up. It is a trip getting 800mm range out of my 100-400. I did lose autofocus which is a bit of a challenge. Seems like it will be fun to mess with.... anyone else have one of these puppies?

Been looking at getting one from y 70-200 2.8, let me know how you like it!

I have the 1.4x, seems ok for slow moving wildlife, a little slower AF, but manageable on my 70-200, don't like it much on the 400 prime because loss of AF. <BR> <BR>Darin you won't lose AF on your 2.8 but will lose a few stops.

Yeah, but I've heard some iffy reviews on loss of sharpness with it vs. the 1.4 which has kept me up in the air. I'm not worried about the stops as I'd use it mainly for outdoor shots.

Yeah, but I've heard some iffy reviews on loss of sharpness with it vs. the 1.4 which has kept me up in the air. I'm not worried about the stops as I'd use it mainly for outdoor shots.

Loss of sharpness with the 1.4 has not been very noticeable on the 70-200 in good light, that lens has sharpness to spare<img src="http://www.wakeworld.com/MB/Discus/clipart/happy.gif" border=0> Have heard that changes with the 2x, that's why I stayed away from it.

The Canon 2X is OK on the 70-200 f4 L IS but not great like the 1.4. It needs a 1 series body and good light to AF with any real success. This is a test shot from that combo on the 1D3.<img src="http://www.wakeworld.com/MB/Discus/messages/87667/748919.jpg" alt="Upload">