I have confirmed using several lenses that the FB Tube is not compatible with the Canon 1D X Mark III.
Works fine with my Canon Rebel T5i/700D.
Re: Canon 1D X Mark III
Posted: 04.07.2020 18:02
by jrhoffman75
Interim follow-up based on some information provided by Catherine - I was able to get the FB Tube to work with the 1D X Mark III if I used Live View. Optical viewfinder setting did not trigger lens focus shift.