Extender EF 2x III Compatibility with EF 400mm f/5.6 L USM Lens

[norrickb]

Will this extender match with my EF 400mm 1:5.6 L telephoto lens?  Will AF work?  I thought the 400 mm was pretty high end expensive when I bought it, but compared to the super telephotos available now I guess it was peanuts.

Maybe I need to upgrade the 400mm?

[ebiggs1]

 I'm convinced the extender isn't what I need.

Agree, it is not a good marriage. A tel-con is almost always a bad idea and or just a  Band-Aid solution. Almost any native FL tele will be better in all regards.  There are a few exceptions but very few and they are all the 1.4x tel-con not the 2x.

[ebiggs1]

"...  I'll just stick with the 400 mm until (if ever) I can afford a new generation super telephoto."

Yours and everybody's  best bang for the buck is one of the 150-600mm super zooms. Save up if need to and buy one of them.