I'm thinking about grabbing a body that will AF quickly at F8 using Canon TCs. My 6D sort of kinda focuses at F8 with my Kenko TC, but the keeper rate is minimal when it comes to any moving target. Does anyone here have experience with these two bodies in combination with a 1.4x TC III? Does the 1Ds MkIII focus as quickly and accurately as the 1D MkIV? Frame rate is not critical to me. Focus speed and accuracy are. The going rate for these bodies used is close enough to be a wash, so the real deciding factor will be IQ at F8 autofocus. Also in the mix at this price is the 5D MkIII, so comparisons to that and the other two bodies is also welcomed.