What Is TTL?
TTL or "Thru-the-Lens" flash metering means the camera evaluates the scene and communicates exposure information directly to the compatible flash. The camera automatically adjusts the power output of the external flash so you don't have to.
This is especially beneficial to people who are still in the learning phase of strobe use - there's enough to worry about underwater without having to manual adjust your strobe output! But even experienced underwater photographers tend to use TTL - it's beneficial to everyone.
TTL exposure is faster and often more accurate than setting the flash output manually. TTL can be the difference between getting a properly exposed image or not, especially when shooting fast-moving subjects and subjects that are moving towards or away from you. TTL is by far the easiest way to shoot perfectly exposed macro photography and allows you to concentrate on focus and framing.
Even if your camera/housing can't use TTL, it can usually be connected to a strobe using manual settings.
TTL Through Fibre Optics
TTL used to be restricted to electronic sync cables, but is now increasingly available using fibre optic cables and TTL flash triggers.
Below we'll go through the different types of TTL available for different underwater set ups. If you're finding it confusing though, just give us a shout and let us know what camera and housing you're using and we can help you out.
This is an evolving space where new products are being released and we expect to see more TTL triggers become availble over time. We'll try to keep it updated as much as possible.
Last updated: 19/09/25
Understanding Your Housing
Flash ports come in three main types:
| Nauticam M11 Fibre Optic Ports - use with appropriate fibre optic cables and flash triggers | Ikelite Electronic Ports - use with TTL Converters and sync cables | Standard Sea&Sea-style fibre optic ports - use with standard fibre optic cables and flash triggers |
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 Above: Nauticam; Below: Ikelite
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Use M11 adapters, or buy Nauticam Universal Optical Fibre Cables
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Most fibre optic cables compatible.
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Congratulations! You will have the easiest time finding a TTL strobe compatible with your system.
OM System and Panasonic cameras that have RC Mode can use a plethora of different strobes without a special trigger or converter, as long as their camera has an onboard flash to trigger, using fibre optic cables. (Yes, this means TG-6/TG-7 users!)
Strobes that have an RC Mode option:
- Sea&Sea DUO
- Ikelite RC165 #40116AU
- Ikelite Ecko (Fibre optic version #40101)
- Backscatter Hybrid Flash (HF-1)
- Backscattter Mini Flash 2 (MF-2)
What you need for these strobes: appropriate FIbre Optic Cables (Sea&Sea, Nauticam or X-adventurer OC-6 recommended); a housing with fibre optic ports, a camera with an onboard flash to trigger.
If your housing has ports for electronic sync cables you can use any Ikelite DS strobes with electronic sync cords (if your housing has ports for them) and TTL converters. Make sure that your bulkhead/hotshoe is the newest version as Ikelite upgraded them circa 2025. (If you're not sure contact us.) If you've got a pre-2025 housing, you may also need a Bulkhead & Hotshoe Upgrade Kit.
If your housing has fibre optic ports, you can use all Ikelite DS strobes with fibre optic cables and RC TTL Receiver.
Canon users have a lot of options due to the wide availability of TTL Flash triggers compatible with them compared to other camera brands.
Nauticam users have the TTL Flash Trigger for Canon #26321 and the dedicated TTL Flash Trigger for Canon II - S (For R6II/R7) #26323.
With these you can use TTL through fibre optics. Make sure that your fibre optic cable has an M11 end to fit onto larger Nauticam housing fibre optic ports (see above images), or just regular Sea&Sea plug for smaller Nauticam housing fibre optic ports. Nauticam Universal Optical Fibre Cable #26216 has both. (Not sure, just ask.)
Those with Ikelite DL or DLM housings can use the TT5 Canon TTL Fibre Optic Transmitter #44701. This will replace either one of your accessory ports, or your flash bulkhead. This is used with fibre optic cables. If you have an Ikelite strobe that only takes electronic sync cords, you'll need a TTL receiver to plug the cables into the strobe.
To use TTL with electronic sync cord, you'll need to use Ikelite's Canon TTL Converter. Make sure that your bulkhead/hotshoe is up to date as Ikelite upgraded them in 2025. If you've got a pre-2025 housing, you'll also need a Bulkhead & Hotshoe Upgrade Kit.
Nauticam users of NA-Z8, Z9, Z6III can now enjoy high speed sync with the HSS TTL Converter for Nikon #26601. (And possibly other cameras in the future.)
If you're using an Ikelite or other housing that has electronic bulkheads, you can use Ikelite's Nikon TTL converter with Ikelite DS strobes. Make sure that your bulkhead/hotshoe is up to date as Ikelite upgraded them in 2025. If you've got a pre-2025 housing, you'll also need a Bulkhead & Hotshoe Upgrade Kit.
You can also use their Nikonos TTL Converter with Ikelite DS Strobes and other brand housings that provide Nikonos N5 connectors (examples include some Aquatica, Nauticam, Subal, Seacam, SEA&SEA, Isotta, etc). Check your housing documentation if you're not sure, or contact us and we can help.
Ikelite are working on a Nikon TTL Transmitter to be used with fibre optic. We expect this will be compatible with all DL and DLM housings.
Sony users sadly have poor TTL converter offerings.
We've managed to track down one Sony compatible TTL trigger, and there's also still Ikelite's converter system if you're okay with electronic sync cords. Make sure that your bulkhead/hotshoe is up to date as Ikelite upgraded them in 2025. If you've got a pre-2025 housing, you'll also need a Bulkhead & Hotshoe Upgrade Kit.
(If you're asking what's wrong with sync cords, the answer is nothing. Some users prefer the simplicity of fibre optic cables, and the ability to unplug them underwater. Additionally, some housings only have fibre optic ports and no electronic bulkheads for sync cords.)
If you want to use fibre optic triggered TTL, the only option that we currently stock is the Backscatter Smart Control TTL LED Nauticam Flash Trigger for Sony. This is compatible with Nauticam Fullframe housings only. We recommend this be used with Backscatter strobes although it does probably work fine with other brands - we just haven't tested it, so can't confirm!
Backscatter also manufacture a Smart Control TTL LED Universal Flash Trigger for Sony. We don't have this in stock, but contact us if you are interested and we can explore whether it's compatible with your system. (It's called universal but nothing's ever that simple is it?) Please allow plenty of time for this, as it will be a special order.
Ikelite are working on a Sony TTL Transmitter to be used with fibre optic. We expect this will be compatible with all DL and DLM housings.
OK, it does get worse than Sony offerings.
TTL for Fujifilm comes in two options, both using electronic sync cables with Ikelite DS Strobes.
If you have an old Ikelite housing for the X-T3, you can try this legacy hotshoe, in combination with the Ikelite Fujifilm TTL Converter.
All other Fujifilm cameras in an Ikelite housing can use the TTL Converter with the regular hotshoe that comes with your housing.
Make sure that your bulkhead/hotshoe is up to date as Ikelite upgraded them in 2025. If you've got a pre-2025 housing, you'll also need a Bulkhead & Hotshoe Upgrade Kit.