I always wondered about a TC on a 5.6 lens
thanksWith my 500 PF, I've found using the 1.4 tele sorta hit or miss. Some turn out OK....others a tad soft or lack the "pop" of the naked lens. The cardinal here came out very nicely. It really depends on how the images will be used. On a cell phone....they will look great. On a large computer screen they will still be OK.
I think the 80-400 is better than the 500pf + tcOne more thought.....I was testing it on both perched and BIF's. AF lock on really suffered using the tele for BIF's. If you know your subjects are going to be relatively still, the tele is a good option if you need more reach. Certainly better than the 80-400 AF-S which doesn't take a tele well at all!! LOL!