70-200 f4 GII plus 2x converter

[Steven Pratt]

Just wondering if all focussing facilities esp tracking is available at 200mm with 2x coverter, i.e. 400mm f8. A7rIV body.

[Cameratose]

Check the low EV requirements for AF. I would think the camera would have no trouble @ f/8, but getting closer to f/13 may be an issue. It's all about light, and like anything else in photography the shutter/ISO/Aperture have to work together. It's impossible to make a blanket statement about the lens and TC only when you consider the other variables.