Hi @Barmaglot, hoping you see this, I just got the 6400 and had some followup questions regarding your very helpful setup notes (I'm coming from an RX100 with 2 YS-D2s):
First, re Live View Display: Setting Effect OFF: I've read this in a couple of other places, emphasizing that if this is on and one is shooting in a dark room/studio with strobes, the WYSIWYG screen will be very dark and thus hard to compose. I totally get that, but in the water if you turn this off, the only way to see your background composition exposure (how blue, how dark, how light, etc.) is to take the shot and see how it looks. And I've never had the scene be so dark underwater that I couldn't compose using Live View (obviously not night dives).
Also, Mark Granger has a really great video about focusing the alpha cameras in low light in which he explains that in AF-C mode Sony lenses will look for focus at the dialed in aperture (and NOT wide open) so if one is stopped down to f8 or 11 or higher, you are depriving the sensor of a lot of light necessary to focus. So his recommendation is to use AF-S in low light, because AF-S "breathes" the aperture and expands it to obtain focus, then shoots at the dialed in aperture. Really great video:
So I'd be very interested to hear how you approach this. I have read elsewhere that one way is to map a Custom key to "Shot. Result Preview" in order to preview the shot:
see link https://helpguide.sony.net/ilc/1810/v1/en/contents/TP0002241284.html
Have you tried that?
Second, why do you set the internal flash to Rear Curtain Sync? Is this because you principally shoot your strobes in TTL? How/would this work if shooting strobes in M?
Finally, can you explain what you mean by your comment that you have C2 set to "WL command toggle ON/OFF for [your] TTL trigger configuration"? What is WL?