I'm new to Canon Rumors and so glad I found it because it's been a great source of knowledge for me. I recently bought a 400/5.6 mainly for birding and wildlife photography. I chose that particular lens because of its relatively low cost compared to the other super telephotos in Canon's lineup. I've been thinking about getting a TC to use in combination with my 7D and 400 for the extra reach but am concerned this combination might not work because of an issue with F8 center point AF I've seen mentioned before. I don't fully understand what this is about but would like to be sure that the TC will work before I spend the money on it. Any enlightenment on this topic is greatly appreciated as I may be totally off base in my understanding.