GMCPhotographics wrote in post #14157913
Here's an odd thing, if I put a 1.4x TC on my 400 5.6 L, it won't AF with my 5DII or 5DIII. But if I put a 2x and a 1.4x TC's onto my 70-200/f2.8 IS L II, it slowly focuses....but not with my other lens. Very odd.
That is odd.
What lens does the EXIF show you are using?
I ask, because I wonder how the AF logic works. Does it check the lens to see what the minimum f/stop is or does it look it up in an internal table?
I ask because I notice in my EXIF, when I use an extender, it shows the lens as: 70-200 f2.8 II w/ 2x ext. (or something similar) I am wondering if it is a table and they designers only allowed for one extender (so one of the extenders is effectively hidden -- or maybe the lens itself is hidden).