Seafrogs a7RIII optical bulkhead

It's a little quiet on the forum, so I thought I'd share results of my latest project.

I just bought an a7RIII and the Seafrogs housing for it. As many of you know, the Seafrogs comes with an electrical strobe connection, but no optical bulkhead for strobe triggering by fiberoptic. I was going to adapt the dual Seafrogs optical connector from their a6xxx housing, which I had done for my a7RII housing, but found that a knob on the a7RIII housing precluded that approach.

My solution was to make a transparent polycarbonate bulkhead to replace the electrical fitting and fire two strobes through it. It works fine with an LED trigger (no TTL) supplied by a friend. It's vacuum tight, but of course, it needs a test in water at depth.

Adapter and retaining nut. LED transmitter on inside and dual fiberoptic connector outside.  Mini-mill and lathe required to make O-ring grooves and notches.  Threads by 1/2-20 die.

Top left-external dual fiberoptic connector. Top right, inside housing, receptacle for LED emitter. Bottom with camera installed.

User3801873999 wrote:

Hi @daveco2,

Any chance you produce these for sale or aware of anyone else making them?

Cheers

UW-Technics TTL converter for SeaFrogs housings comes with a replacement optical bulkhead that incorporates a triggering LED, but it's fairly expensive at $450.

kelpdiver wrote:

using the camera flash or a flash trigger is a pain in its own right, esp with the S&S strobes.

I'm curious as to why.   I've only had experience with YS-D1's and optical triggering so don't see why it's a pain.   I used the pop-up flash on a D810, and now a Nauticam LED trigger with a D850.

I sync just fine to 1/200th, but trying for 1/250th generally gives me a black line of shade.

But they've always triggered just fine, even when new and I used an RX100 II (pop-up flash) with them.

kelpdiver wrote:

weird to see an electrical only these days. more common to see optical only.

The Sony A7/A9 series don't have a built-in or bundled clip-on flash, so the SeaFrogs housings ship with an electrical bulkhead that plugs directly into the hot shoe. Their A7S III housing does have optical ports that are aligned to work with a simple trigger that they sell for $20, in addition to the normal electrical bulkhead.

PHXAZCRAIG wrote:

kelpdiver wrote:

using the camera flash or a flash trigger is a pain in its own right, esp with the S&S strobes.

I'm curious as to why. I've only had experience with YS-D1's and optical triggering so don't see why it's a pain. I used the pop-up flash on a D810, and now a Nauticam LED trigger with a D850.

The optical sensor on YS-D2 strobes is significantly less sensitive than the one on YS-D1, and YS-D3 is worse than YS-D2 in this regard. Sea & Sea's own trigger for D3s uses twin AAA batteries and eats through them quite quickly, just to power the LED that is strong enough to drive these strobes - compare that to more common triggers that run for months on a coin cell battery.

User3801873999 wrote:

Hi @daveco2,

Any chance you produce these for sale or aware of anyone else making them?

Cheers

I made the connector only after I was able to identify a transmitter.  So, I would say the transmitter comes first.  I tried a number of them.  Some wouldn't fit between the hot shoe and case, and others didn't have enough intensity to trigger the Z330.  I finally wound up with a custom, one-off unit from a fellow in New Zealand.  It's trigger only, no TTL.  That was a couple of years ago.  Things may have changed.

I finally bought the UW Technics unit for its TTL.  Since then, I've determined that I can operate manually, which many others suggested as a preferred approach.

If you have a transmitter, you could email Pavel at UW Technics and ask if he'll sell the bulkhead connector only.  Or go for the expense of their unit.  Let me know if none of the above work.

Barmaglot_07 wrote:

PHXAZCRAIG wrote:

kelpdiver wrote:

using the camera flash or a flash trigger is a pain in its own right, esp with the S&S strobes.

I'm curious as to why. I've only had experience with YS-D1's and optical triggering so don't see why it's a pain. I used the pop-up flash on a D810, and now a Nauticam LED trigger with a D850.

The optical sensor on YS-D2 strobes is significantly less sensitive than the one on YS-D1, and YS-D3 is worse than YS-D2 in this regard. Sea & Sea's own trigger for D3s uses twin AAA batteries and eats through them quite quickly, just to power the LED that is strong enough to drive these strobes - compare that to more common triggers that run for months on a coin cell battery.

Good to know.   I have three YS-D1's now, all used for a while.  (I bought two used ones well over a year ago to replace a dead one, and I've actually still not even tried them.)

I've thought a lot about what I would get to replace the YS-D1's, especially after all the negative press about YS-Dx models.   Thinking Retra.   I don't know of other strobes with flash power of YS-D1.

As far as power goes, you've got choices - Inon Z-330 is an obvious one, but also OneUW 160X, even Seacam 160D if you have money to burn. Ikelite's DS160/161 is getting long in the tooth, but the replacement model is supposed to come out soon - they've showcased prototypes as far back as DEMA 2019. As a Retra user, I can honestly claim that you can't go wrong with them, but they're far from the only game in town. Even Weefine/Kraken produce a strobe now, although its main selling point is long battery life on a quad-pack of Li-Ion 18650s - otherwise it's somewhat feature-deficient.

User3801873999 wrote:

Thanks @daveco2,

I actually have the Turtle S-TTL trigger and have used i for a number of years on my saltedline a6000/s6400 with no issues on both YS-D2 and YD2J's.

I had been harassing the sales guys a Seafrogs for a couple of years to bring back the optical port on the A7iii, but it looks like that ship has sailed.

I've not yet purchased the A7iii housing, but it looks like I will get one soon as I feel this polycarbonate bulkhead fitting will solve the issue. I've spoken to Balazs at Turtle and he can make a single LED cable to suit the PC bulkhead.

I've made a 3d CAD model of the bulkhead off the information i've found in web searches and intend on having a number made up in production (due to minimum order limitations). I'll wait for my housing to arrive before committing to production, just to make sure the dimensions are correct.

Will take a little while, but i'll report back with how I get on.

Excellent, looks like you have a good path.

A couple of comments:

I made my connector out of lexan (polycarbonate) because (a) it has the strength to withstand the force of the retaining nut without shattering or distorting as the connector is drawn down to compress the O-ring, and (b) it can be polished at the bottom of the fiberoptic wells for maximum light transmission.

I started with acrylic but quickly found it to be too brittle to be machined or to withstand the force of a bolt.

A few more views.

Case dimensions surrounding the port. Dimensions inches.

Internal view of open port. Black bulkhead with two holes mates with later mod to incorporate dual fo ports of the SeaFrogs style.

External view of open port. Note flats either side that prevent turning when the nut is tightened.

Stock electrical bulkhead fitting.  Reattached to provide alternative electrical connection, in addition to newly added SeaFrogs twin optical port at the front.