CHG_CANON wrote:
As others have noted, the specific details probably determine what / why one of two extenders are used.
If the 2x with lens and camera model can't autofocus, that kind of the ends the 2x discussion for that lens and camera combo.
If the 2x with an f/4 lens and camera model provides AF only with the center AF, the photographer might find that too limiting.
Uh..... I have both the 1.4 and 2.0 on Canon. Both autofocus. I use each one depending on the situation and how much extra reach and light needed/available. I have also stacked them and maybe it's just my luck - but that autofocus works well also. They are inexpensive if purchased used, and I would try them out before you take advice from incorrect sources. Used, on canon 70-200 IS 2.8, and canon 300 2.8.