Thanks for yours comments….I never see the preflash unless I look for it. It is one of the downsides of Sony cameras. In fact, as much as I like my camera, I would probably just buy a Canon GX7III or the AOI Oly rig or a Nauticam with the Oly OM before considering any Sony camera. I do not know if the FF Sony cameras have a preflash cancel or a fully manual flash selection as do Oly, Canon, Nikon. But the A series Sony cameras alway fire a preflash even in manual mode.
If the ST100 strobes cannot be set for a preflash then they will not work with a Sony camera. No way, no how. Any modern strobe from Inon (S220) or YS, S&S, Backscatter, Retra, whoever, will be able to configure for a preflash (except for Ikelite stuff possibly).
I have been using Inon D2000 strobes but just bought a set of Inon S220 for their smaller form factor and slight power increase.
How is your opinion of INON S220?