So you are saying the the GH5 does not have enough HP to handle its recording functions AND auto focus without using an external recorder?
This should not come as a big surprise as auto focus is worse in 4K mode vs HD mode also on the GH4.
Apparently the auto focus works even better if you don't record at all.
Please see page 166 in the "Operating Instructions for Advanced Features" for the GH5:
"To ensure highly accurate focus, 4K motion pictures are recorded at reduced auto focus speeds. It might be difficult to focus on the subject with Auto Focus, but this is not an malfunction."
Sine auto focus seems to be substantially better as long as you don't record anything, this suggest that the CPU runs out of steam during actuall recording. Even more so in 4K mode.
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