Pavel Kolpakov

Actually, some Nikon cameras allow "Rear curtain sync" option, only if recognize TTL protocol (flash, or TTL-Converter). But i am not sure regarding D500.

Hi Elmer, Here is a picture of installed TTL board for Nexus Nikon (product #11063 UWTechnics):

The best transmission index have 613-core fiber optical cables: Nauticam #26216, #26217, or HowShot 613L.

Hello Dan, UW Technics produces Optical and Nikonos bulkheads for Ikelite housings (for usage with UWTechnics TTL-Converters). Optical Bulkhead is here: Your housing has 2 holes on the top. So, you can install 1 or 2 optical bulkheads, dependently on preferences. TTL-Converter supports maximum: 2 optical + 2 electric bulkheads, simultaneously. On this housing you even can use 1 optical + 1 electric bulkhead, both in TTL, if you want to use different strobes. TTL-Converter board shape for this housing model is in development yet, but will be announced soon. Firmware as usual includes ttl-profiles for Inon, Sea&Sea, Ikelite and Subtronic strobes. Retra ttl-profile will be included too, when new strobe appears on the market.

This TTL-Converter is purposed for installation instead of Seafrogs leak detector in the housing. That is why, it includes also a Leak Detector onboard, in addition to TTL electronics. By the way, the Leal Detector is better than original. You can connect Optical bulkhead or Electric bulkhead to TTL-Converter, dependently of your preferences. TTL works the same in both variants. In case of Optical bulkhead, you can use HowShot 613L or Nauticam #26216 fiber optical cable. Those are new 613-core cables with the best transmission index now. Dual FO cables are supported as well. In case of Electric bulkhead, you can use Sea&Sea (Nikonos) or Ikelite sync cord. Dual sync cords are supported as well. Original Seafrogs electric bulkhead (factory preinstalled) does not have enough pins, it cannot be used in TTL system. Regarding TRT products, please ask manufacturer directly. Sorry, I don't have enough technical information.

UWTechnics currently produces Optical Bulkhead and Electric (Ikelite, Nikonos) bulkheadfs for Seafrogs housings. Those bulkheads have special shape mount side, the same as Seafrogs / Meikon original. TTL circuit for Sony A7-A9 Seafrog housings:

Z240 performs just a mono flash, it cannot produce FP flicker 40 khz. Camera shutter window must be fully open at the moment of mono flash, to get uniform exposure along the shot. Nikon mechanical shutter fully opens window maximum at 1/250, not faster. That is why 1/250 is official "sync speed". If user sets 1/320 ... etc., the window never fully opens, it looks like an open strip going along the shot (rear curtain becomes visible on the picture), and it needs FP flicker long flash then. So, shooting by Nikon with underwater strobes, user must set only up to 1/250 speeds, to get uniformly lighted picture. Yes, 1/320 is threshold value, dark strip is slightly visible (or almost invisible) on some Nikons, but anyway, it is not recommended for common case.

This is truth, Inon FEC algorithm via Z240 / Z330 right dial switch is effective not for all cases. Synching by pop-up flash, the effect sometimes is small or invisible. But, if you use any Optoelectronic TTL-Converter for Z240 / Z330 synchronization, you see that Inon FEC (right dial switch) really adjusts +/- lighting. This is because of LED's clear square signal shape, Inon FEC algorithm process it much better than analog flash signal.

Yes, Retra new strobe is announced as HSS. We are waiting for it to make TTL tests. When HSS strobes appear on the market, TTL circuitry manufacturers can make HSS feature in firmware.

Thank you for kind words guys! I am happy to help when i can.

Thanks for the info guys!

Good job! And good idea! Please advice, where did you buy that transparent spare part? I also need it. By the way, UW Technics is developing now TTL converter for Seafrog A6xxx housings. It's LED board is purposed for installation on this transparent part (inside the housing). TTL converter has LED and Electric outputs, as usual. So, you could more easy use both type connectors (Optical/Electric) on your A7RIII housing, using that transparent part you has installed and Nikonos bulkhead simultaneously.

I sent you few suggestions by messenger. Please look.

The concrete strobe YS-D2 sample may be a problem, who knows. Try to change the strobe, just for test. Let's contact in Messenger, I think i know how to solve your setup problem anyway.