We went to Orlando Wetlands Park, then to Merritt Island bird refuge. I was using my tammy 150-600, then he let me use the 400 f4 DO II, then I put a 2x teleconverter on it. Dark overcast really challenging conditions.

Well..... the AF is just really fast, even w/ the TC. The IQ is more than crazy good. I am sure he will be posting some higher res pics soon.

800mm wide open (f8) hand held about a 1/3rd crop.

Feb 4 10 by mbarrett5076, on Flickr