Tested the combination with my Canon 500mm f4.0 on static subjects.
Unlike before the newest firmware update focusing was almost non-existent.
The focus mechanism was active but just ground uselessly back and forth and never focused.
Today the focus was very snappy, possibly almost as fast as a Canon 5D mark III.
Using my tele-extenders with the - nothing happened at all.
I did not have time to do a fuller test with moving subjects but tomorrow I will have an opportunity.
I still don't expect the overall AF to be anywhere near as usable as the Canon 5D III with long lenses.
Tony Jay
