Originally Posted by
Daniel Browning
Think of the 7D as a perfect 1.6X TC. It doesn't add any additional aberration, it doesn't slow down (or stop) autofocus, and it doesn't make the viewfinder any darker. All it does is magnify the flaws in your lens. Since the 500mm f/4 has few flaws, this is not much of a problem. I would have thought that the 7D would handily trounce the 5D2+1.4X TC, because real life teleconverters aren't perfect (though their distortion and chromatic aberration can often be corrected in post), but in this case (200mm lens) it looks like even with the 1.4X TC, the 5D2 is sharper: