Does anyone here use two 1.4X extenders? If so, can you tape one set of pins and say focus at f8 on a canon ef 400 L f5.6?
Right now I use a 5d mk iii and I find it quite capable with the extender taped . I guess I am thinking, when the new firmware comes in the spring, can I feasibly have a 800 f8(f11 reality)?
I've used the 2xII with a 100-400L for 800mm f/11, on a 7D and 5DII. Focusing was difficult even on a tripod. Optical quality was not great, contrast was very low. Stacked 1.4x TCs would be worse.
I've used the 1.4xIII with the 100-400 on the 1D X, AF worked, and optically the results were quite decent.