Review: e-Turtle Smart 3 Manual Flash Trigger for Canon cameras
Forewords
Since switching to Canon in May 2025, I’ve had the opportunity to test four different flash triggers on the Canon R5 Mark II, which is the camera I’ve been using for this review. Like most photo gear, each came with its own set of strengths and compromises, but none fully met all my “must-have” criteria: maximum sync speed, burst performance, battery life, and overall convenience.
In hindsight, and after researching the topic more deeply, I’ve come to suspect that Canon’s flash system may be more complex than those of competing brands. This seems to make it more challenging for third-party manufacturers to design flashes and triggers that provide full access to Canon’s flash functionality. That challenge may be further compounded by Canon’s recent hot-shoe redesign: starting with the EOS R3, newer Canon bodies feature a revised multi-pin flash connector.
This ongoing search for a more complete solution eventually led me to TRT Electronics’ latest Canon trigger: the eTurtle Smart 3 Manual trigger, which is the subject of this review.
Acknowledgements: I want to thank TRT Electronics for providing a Smart 3 Manual flash trigger, for the purpose of writing this review.
About TRT Electronics
TRT Electronics is a well-known name in the small world of underwater flash triggers. The company is now shipping its third-generation triggers with variants for Canon, Olympus/Panasonic, Nikon and Sony, following several iterations that refined functionality and improved battery life.
At the time of writing (early December 2025), Olympus/Panasonic, Nikon and Sony shooters can choose between manual and TTL versions of the TRT3. Canon users, on the other hand, only recently gained access to the manual version reviewed here, with a TTL variant to start shipping in the coming weeks.
Before we go any further
In this article, I am assuming you’re well familiar with fundamental flash concepts such as maximum sync speed, high-speed sync (HSS), or second-curtain synchronisation.
If any of those terms feel unclear, head over to our Underwater Camera Settings course, where I explain the various flash controls which let you fire a strobe, and how they matter for underwater photography.
Maximum Synchronization Speed
First things first: the Smart 3 trigger consistently synced at the Canon R5 Mark II’s maximum flash sync speed of 1/250 s. With some of the triggers I tried, you would see parts of the image not receiving strobe light when shooting at 1/250th, and would have to dial down the shutter speed for fully flash-lit photos, so this is a first thumbs for TRT Electronics’s product.
Remark: the camera must be set to Electronic First Curtain shutter mode to synchronize at that shutter speed. This isn’t specific to the Smart 3 trigger — even Canon’s own Speedlite flashes are subject to lower sync speeds when using other shutter modes on recent Canon mirrorless bodies.
Burst Speed
In Electronic First Curtain mode, the Canon R5 Mark II tops out at 12 frames per second, and I found that the Smart3 manual trigger sustained that rate without missed flashes.
It may well be capable of even higher burst rates on other camera bodies, but I wasn’t able to test that. While the R5 II can shoot up to 30 fps, doing so requires switching to full electronic shutter (electronic front and rear curtain), in which mode the Smart3 manual trigger dropped to around 6–7 fps.
This trigger appears optimised for a specific shutter mode, and I’m glad TRT Electronics chose Electronic First Curtain. In full electronic shutter mode, the R5 II’s maximum flash sync speed drops to 1/160 s, making it far less relevant for strobe-based underwater photography anyway.
As discussed in my Canon R5 Mark II review, Electronic First Curtain remains the most practical shutter mode for underwater photographers using strobes — and it’s reassuring to see the TRT3 designed around that reality.
Battery Life & Maintenance
I’ve probably written this in most of my reviews: I’d rather spend time looking at my photos than looking after my equipment, and manufacturer that makes it quicker to maintain their products earns immediate goodwill in my book.
TRT Electronics’ third-generation triggers bring a substantial improvement in battery life, along with a helpful battery-status indicator. Press a button, and a sequence of LED blinks shows remaining charge in 25% increments. There’s also a dedicated on/off button, allowing you to shut the trigger down completely when it’s not in use.
Here’s what I observed during my testing:
After a full charge, I managed to fire over 10,600 shots while still showing more than 75% battery remaining. This test involved running the camera on an intervalometer with a strobe firing into a bucket of cold water until the camera battery was exhausted — the trigger itself barely seemed to notice, while I had to swap camera batteries twice.
Encouraged by that result, I then tested a more realistic “forgetful diver” scenario. I left the trigger switched on continuously — connected to the camera — over a ten-day period during which I did three long dives (about 3 hours each). At the end of that time, the battery indicator had only dropped to the 50% mark.In practice, this means you could charge the trigger at the start of a dive trip and comfortably forget about it for the rest of the trip. If you ever did find yourself short on power, the TRT3 conveniently ships with a spare battery.
Installation
The TRT3 trigger comes with two optical connectors that attach to the housing’s fibre-optic ports using double-sided tape. Installation was straightforward, and after six weeks of use, neither connector showed any sign of coming loose.
The main trigger body can be disconnected from the fibre-optic cables if needed — for instance, during charging. However, given how infrequently charging is required, I found it easiest to leave the entire assembly installed permanently in my Nauticam housing, and simply connect a long USB-C cable when a charge was needed.
HSS
The TRT3 is HSS-capable, which I confirmed works with the Retra Pro Max II strobes which I had on hand. Unfortunately, testing coincided with less-than-ideal diving conditions, so I wasn’t able to capture images that meaningfully demonstrate HSS underwater.
It’s worth noting that you need to configure the shutter speed at which the trigger switches into HSS mode. This threshold is camera-dependent and can be set easily using TRT Electronics’ Mac/PC application, with the trigger connected via USB-C.
Second Curtain Synchronization
Canon cameras default to first-curtain sync and only allow second-curtain sync when a compatible Canon flash is detected. This limitation is one of my few ongoing usability frustrations with Canon’s system. Until now, it seemed that only TTL-capable triggers could effectively “pretend” to be Canon flashes and unlock this setting.
To my surprise, the Smart 3 Manual trigger does allow access to second-curtain sync. This is particularly useful at slower shutter speeds, where you want motion blur to trail behind a moving subject rather than appearing unnaturally in front of it.
One caveat: when the camera enters sleep mode, flash settings revert to first-curtain sync. If you plan to work extensively in second-curtain mode, I recommend temporarily adjusting your camera’s power-saving settings. I detail how I’ve customized my Canon R5 II for underwater use in this article.
TRT Electronics has confirmed that the upcoming Smart 3 TTL version will maintain second-curtain sync even after the camera goes to sleeps.
Conclusion
Overall, the e-Turtle Smart 3 Manual trigger for Canon is a well-rounded and thoroughly dependable flash trigger that performed flawlessly throughout six weeks of testing.
It reaches the R5 Mark II’s maximum sync speed, sustains burst speeds of at least 12 fps, and offers outstanding battery life — making it not only easy to install, but also low-maintenance. The rechargeable battery is a welcome environmentally-friendly feature, and the inclusion of a spare adds redundancy. The trigger also offers HSS support and access to 2nd curtain sync (with a caveat, read the previous section) which were nice bonuses, normally expected on TTL-capable triggers.
Beyond the product reviewed in this article, TRT Electronics is a company that keeps innovating (check their recent product announcements on Facebook/Instagram), listens to their customers and are open to feedback. I’m looking forward to seeing what they release next — and to testing the forthcoming TTL version of the TRT3 for Canon, expected in early 2026.
About the reviewer
Nicolas Remy is an Australia-based pro shooter and founder of online underwater photography school and community, The Underwater Club, with members in 26 countries. He serves as an ambassador for Mares and Nauticam, and chairs the jury of the prestigious DPG Masters photo competition. Nicolas’ images have been widely published in print and digital media, and have won over 40 international photo awards. To see more of Nicolas’ work or browse his upcoming workshops, visit: www.nicolaslenaremy.com.
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