russbecker wrote in post #18653690
I have a Kenko DG version of this converter, which is excellent (just spent a week testing it against the Canon 1.4X III and couldn't tell the difference at f/8, f/9).
You are saying that the DGX version will
not work with a 7D2/80D at f/8 (presumably it will at f/5.6 with all bodies). I am looking to pick this up as a second converter to use principally with a 300mm f/4L or 70-200 f/2.8L while I use the DG series one with the 100-400 Mk2 on my 7D2.
Getting tired of swapping lenses...
No; I mean it can turn a 7D2 into a paperweight that won't take pictures at all, or takes them but disables IS, or any number of strange phenomena. It was only designed for Canon bodies that already existed at the time it was designed, and had no guaranteed forward compatibility. It goes outside of normal TC protocol, which is to only talk to a lens that has the TC pins (not all do), and not to the body. The DGX intercepts the signalling that normally occurs only as pass-through between the body and lens and changes it, The signalling or timing apparently changed with some new cameras and the DGX's assumptions are wrong, and interfere with camera functioning.
I don't remember or know all the details, but I do know that I and many others can't use it with the 7D2 or the 80D, and possibly some other newer (only f/8 AF ones, maybe?) cameras. What it is guaranteed to do right is work like magic on older bodies, with older lenses (I don't remember if new lenses on older bodies is ever an issue off the top of my head).
For anyone using older f/5.6 cameras and older lenses, you can be sure that this TC delivers all the magic it is supposed to, and is a steal at $65, even if only for correct EXIF data for manually-focused optics with two stacked TCs. Just don't assume it will work with newer bodies, especially. I was very sad to lose what it did on my 7D when it didn't work with the 7D2. On the 7D or 6D, I'd choose it over the Canon 1.4xIII if I could only have one or the other.