It seems to be a trade off. As you stop down the lens, the corners are sharper on III but softer in the center vs II. Looks like a hair more CA is evident in the mkII as well.


The verdict is still out on this combination (based on the crops alone). I was able to snag possibly the last *out of stock* available for purchase 1.4x II on amazon for $276. A bargain I suppose compared to $499 for mkIII, especially for occasional use. I