can anyone answer these questions for me.
will 1DIII auto focus with the canon EF 1X4 attached to 100-400L, 200 F2.8L prime (mark 1) and how much degradation with the 100-400L?
Yes on the 100-400, and here are some photos: https://photography-on-the.net/forum/showthread.php?t=915950
200 f2.8l should be just fine. 1D bodies will AF with any combo up to an f/8 maximum aperture.
got a 100-400 by any chance?


