I already read Bryan's review of the new 400. I was surprised by the results Bryan got with the AF.


Quote Originally Posted by Bryan Carnathan
I have used three different Canon EOS 1Ds Mark III DSLR bodies behind the 300 IS II and 400 IS II and have shot numerous sports events (along with the galloping horses and running kids at home). To be honest, I had a somewhat better AI Servo in-focus rate when using the original version 1 IS lenses.

It sounds like what he said applies to the new 300 as well, but I have had no problems with the AF at all. Any OOF shots I get with it are usually my fault. The bare lens is amazing, besting even the 70-200 II in AF tracking. It's slower to obtain focus lock with the 1.4x and even slower with the 2x, but that's what I expected. It seems to have no trouble tracking afterward, though I've only tested this with slower moving targets. Perhaps with faster moving targets Bryan's lens was anticipating too much between frames, so by lowering the speed a little he was able to improve keeper rate.


I was also surprised by the ISO12233 crops from the 400 II. The ones with the 2x III actually look worse when compared to the 400 I. I'm not sure what to think about this, considering that the 300 II does so well on the charts and, from my personal experience, in real life.


Quote Originally Posted by HDNitehawk
Here is a thought, if the 500mm II puts out acceptable performance with the new 2X III and the 600mm with the 2x III just doesn't give the IQ I am looking for, the 500mm would be the longer lens for me.

That is a good point, though I wonder how much worse the 600 II + 2x III would have to be to outweigh the fact that you're at 1200mm vs 1000mm. The 2x is acceptable, but I find myself wanting to go to f/8 since the improvement is noticeable in real world photos. If I wasn't photographing subjects at such a distance where I needed to crop maybe I wouldn't care as much. Here's a 100% crop from a photo I took just the other day with the 300 II + 2x III @ f/5.6 ISO 1000 on the 7D (normal settings in Lightroom, no other changes made):





For a 100% crop from the 7D, the image actually isn't bad, but I'd really like to fill the frame more and have the image be a little sharper. I'll be trying to move closer to the birds to fill more of the frame, but even then more focal length would certainly help. I'd love it if the 2x on the 600 II would provide great results, and maybe I could try and use live view to manually focus it (or tape contacts) since I don't own a 1DIV. I don't want to count on using autofocus at f/8 since it looks like that won't be an option on future bodies, particularly since I've been using the 7D for the crop factor and likely will continue to want to use 1.6 crop bodies.