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The author would like to thank TRT Electronics for providing an e-Turtle Smart 3 Manual Flash Trigger for the purposes of this review.
 

Since switching to Canon in May 2025, I’ve had the opportunity to test four different flash triggers on my Canon EOS R5 Mark II. Like most photo equipment, each trigger 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 e-Turtle Smart 3 Manual trigger. The company is now shipping its third-generation triggers with variants for Canon, OM System/Olympus/Panasonic, Nikon and Sony, following several iterations that refined functionality and improved battery life. At the time of writing (early December 2025), OM System/Olympus/Panasonic, Nikon and Sony shooters could choose between manual and TTL versions. 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. (Look out for my review of the TTL version on DPG soon.)
 

At the end of October, I took delivery of a DPG-branded trigger! A nice touch from TRT Electronics

Installation

The Smart 3 Manual trigger comes with two optical connectors that attach to the housing’s fiber-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 fiber-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.
 

Two “rings” of red double-sided tape (provided with the trigger) stick on the black discs towards the end of the optical cables, which then attach to the housing’s two fiber-optic ports

Maximum Sync Speed

First things first: The Smart 3 trigger consistently synced at the Canon EOS R5 Mark II’s maximum flash sync speed of 1/250s. With some of the triggers I tried, you would see parts of the image not receiving strobe light when shooting at 1/250s, and you would have to dial down the shutter speed for fully flash-lit photos. So, this is a first thumbs-up for TRT’s product.

It’s worth noting that 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 R5 Mark II tops out at 12 frames per second, and I found that the Smart 3 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 Mark II can shoot up to 30fps, doing so requires switching to full electronic shutter (electronic front and rear curtain), in which case the Smart 3 dropped to around 6–7fps.

This trigger appears optimized for a specific shutter mode, and I’m glad TRT Electronics chose Electronic First Curtain. In full electronic shutter mode, the R5 Mark II’s maximum flash sync speed drops to 1/160s, making it far less useful for strobe-based underwater photography. As discussed in my 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 Smart 3 specifically designed around that reality.
 

Battery Life and Maintenance

I’ve probably written this in most of my reviews, but I’ll say it again: I’d rather spend time looking at my photos than looking after my equipment, and manufacturers that make it quicker to maintain their products earns immediate goodwill in my book. TRT’s 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 power the trigger down completely when not in use.
 

With the trigger switched on, long press the white button and the red LED next to it will blink to indicate remaining battery life
 

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 10-day period during which I did three long dives (about three 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 Smart 3 conveniently ships with a spare battery.
 

High-Speed Sync (HSS)

The Smart 3 Manual is HSS-capable. I confirmed it does indeed work using the Retra Pro Max II strobes that 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 camera-dependent threshold is set easily using TRT’s Mac/PC application, with the trigger connected via USB-C.

Second Curtain Sync

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. In my experience, it seemed that only TTL-capable triggers could effectively “pretend” to be Canon flashes and unlock this setting, so I was surprised to find that 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.
 

Left: First-curtain sync—motion blur appears ahead of the fish. Right: Second-curtain sync—motion blur trails behind the subject, producing a far more natural result. (For illustrative purposes only)
 

The Smart 3 Manual trigger gives you partial access to the Canon speedlite menu, where you can toggle between first and second curtain sync
 

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 EOS 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 sleep.

Final Thoughts

Overall, the TRT Electronics Smart 3 Manual trigger for Canon is a well-rounded and thoroughly dependable flash trigger that performed flawlessly throughout six weeks of testing. Both easy to install and low maintenance, the trigger supports the Canon EOS R5 Mark II’s maximum sync speed of 1/250s, sustains burst speeds of at least 12fps, and offers outstanding battery life. The rechargeable battery is a welcome environmentally-friendly bonus, while the inclusion of a spare adds redundancy.

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 Smart 3 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 18 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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