Can I use rear sync?

[Steen N]

Hi everybody.

 

I was planing to play around with slow shutter and rear sync. But when I connect the flash trigger to the hotshoe on the camera, the rear sync option disappears in the camera menu.

I use a Sony a7r4 in Nauticam housing. Strobes are Retra pro X, and flash trigger are UWT.

Is there a setting I am missing? Or am I just not able to do rear sync with this combo?

Hope anyone knows.....

 

Steen