Strobe help please

Hi everyone,

I've been using my Sony a7Riii and the Seafrogs housing for snorkelling (previously had the a7Rii with a Seafrogs housing and used it on a few dives which was also awesome) and it's been fantastic but I'm looking to expand this to some scuba diving and I'll need some strobes. The issue is which ones...

Obviously the Sony a7Riii doesn't have a pop-up flash so that somewhat limits my options as far as my research goes...? The Seafrogs housing has a connection from the hotshoe to a port at the top which has 3 pins (see attached image below).

Am I limited to using strobes which have electrical connections (sync ports) only? These strobes tend to be very expensive when compared to other cheaper fibre-optic options. Also, I'd like to future proof it and maybe add a 2nd strobe in the future - if electrical sync ports are my only option, is it possible to have one strobe connected to the sync port and connect that strobe to a second strobe using a fibre optic cable (ie. daisychain them)?

Many thanks in advance for any help!

Pavel Kolpakov of UW-Technics posted some time ago that he's planning to have a replacement bulkhead to allow for fiber optic triggering instead of sync cords with these housings, but I don't know where he's at with this - you might want to get in touch with him and inquire about it. He has finished developing the Sony-specific circuits some time ago, and my order of a Sony/SeaFrogs UW-Technics converter is currently in the mail, but it's for an A6xxx Salted Line housing, so not directly relevant.

Thanks for your response. So would this bulkhead replacement convert the electronic signal into some kind of fibre optic signal? Sounds exactly what I'm after! Do you have any answers to my other questions? ie. If I don't get this replacement bulkhead, my only option is to go for strobes which using sync cords? Do I need a sync cord splitter or can I run a sync cord to one strobe then a fibre optic connection from that strobe to another strobe?

John P_AU wrote:

Thanks for your response. So would this bulkhead replacement convert the electronic signal into some kind of fibre optic signal?

No, it would just allow you to attach a fiber optic cable - you would still need an LED to generate the optical pulses. This can be either a simple trigger that would only allow you to run manual mode, or a TTL converter such as one of these to enable TTL operation.

Sounds exactly what I'm after! Do you have any answers to my other questions? ie. If I don't get this replacement bulkhead, my only option is to go for strobes which using sync cords?

Either sync cords, or an external converter .

Do I need a sync cord splitter or can I run a sync cord to one strobe then a fibre optic connection from that strobe to another strobe?

A dual sync cord would be easier to work with. Daisy chaining with fiber optics is, AFAIK, only done on Sea & Sea strobes; Inon Z-240/Z-330 don't have the appropriate sockets.

Note that running a sync cord from the housing to strobes and plugging the internal connector into the camera's hot shoe will only allow you to use manual operation with whatever strobes you pick. If you want TTL, you will need the appropriate converter even if you stick with sync cords.

Barmaglot_07 wrote:

Note that running a sync cord from the housing to strobes and plugging the internal connector into the camera's hot shoe will only allow you to use manual operation with whatever strobes you pick. If you want TTL, you will need the appropriate converter even if you stick with sync cords.

Wow, this is really surprising. I thought I'd get TTL using the hot shoe-sync cord-strobe... This really makes trying to plan this system a pain in the backside. Apologies for the questions but why wouldn't TTL work with the sync cord connected to the strobe?

John P_AU wrote:

Wow, this is really surprising. I thought I'd get TTL using the hot shoe-sync cord-strobe... This really makes trying to plan this system a pain in the backside. Apologies for the questions but why wouldn't TTL work with the sync cord connected to the strobe?

TTL via hotshoe requires bidirectional communication between strobe and camera, and each camera manufacturer runs their own proprietary protocol. Seacam Seaflash strobes and the newer OneUW 160X have the TTL circuitry inside the strobe, but as the result you must order them in either Canon or Nikon versions, which will only work correctly with the appropriate cameras. For other systems, a TTL converter that attaches to the hotshoe provides the interface between the camera and the strobe(s).

Makes sense now. Thanks for this really easy to understand explanation mate