Quote Originally Posted by Busted Knuckles View Post
The TCs are different optical formula. Post vs pre adapter
As Brant pointed out the 1200mm RF 2x is is much better that the EF 1200 EF 2x III.

If Canon holds true to form I bet the performance (including speed) is equal or better with the new than it was with the old.

One thing that concerned me was the lack of noise from the IS system. Bryans review said there is an audible click and noise that you can hear. I haven't been able to hear it at all, even with my ear against the barrel. So I keep retesting it. I saw a video on the internet where the reviewer was talking about shooting at a shutter speed of 1/6 hand held and could read the print on the target. I gave it a try on the wife's shampoo and sure enough hand held I could read the print with IS, and no go without. I wonder if this one point is a carry over from the EF III review that didn't get updated.