Turtle SMART TTL Converter and Flash Trigger Review

The Turtle SMART TTL converter is an elegant way to fire your underwater strobes rapidly and with accurate exposures every time!
By Mark Hatter

The Turtle SMART TTL trigger is an ingenious device capable of triggering underwater strobes with lighting quick recycle times and accurate exposures. This flash trigger works with most underwater housings. They are available for use with most underwater strobes on the market and most cameras - particularly popular brands like Nikon, Canon, Sony, and Olympus. We had photojournalist, Mark Hatter, and Underwater Photography Guide Editor-in-Chief, Nirupam Nigam both take some Turtle Smart TTL triggers underwater and put them to the test. Before we get into the results, lets take a brief moment to describe the problem solved by TRT-electronics. 

The Problem

In order for a strobe to fire, it needs to properly sync with the shutter mechanism on the camera. There are two basic ways of doing this:

  1. Electronic sync cords connect the camera to the strobe via the hotshoe mount on the camera which sends an electrical signal through the cable to the strobe. This requires a bulkhead on the housing for the cable to connect to, and the camera connects to the bulkhead through circuitry that attaches to the hotshoe. The benefits of are quick recycle times that aren't limited by a camera's onboard flash. However, syc cords are only capable of TTL exposure (e.g., automatic strobe exposure) if a TTL converter is added to the circuitry. 
  2. Fiber optic cables connect the camera to the strobe by capturing an optical signal from the camera's built in flash and sending it to the strobe. Fiber optic cables usually connect externally to the housing via a glass optical port (i.e., it won't flood). They are capable of transmitting TTL signal if the camera is triggering the strobe via an onboard flash. However, fiber optic cables can be limited by the built in recycle speed of the camera's flash. In order to increase recycle speeds, underwater photographers need an LED device called a flash trigger which is often not capable of TTL. 

Whether sync cords or fiber optics are the best way to trigger a strobe has long been debated in underwater photography.


The Solution

The Turtle SMART TTL trigger solves the limitations of both sync cords and fiber optic cables! Sync cord users can use the Turtle TTL trigger as a TTL converter that attaches directly into the hotshoe of the camera and connects to the sync cord bulkhead in the housing. This gives sync cord users TTL capability when they shoot underwater to get proper exposures with every shot - no matter the distance the shooter is from the subject. 

Fiber optic cable users will be able to replace their on board flash and use the Turtle SMART TTL trigger as a flash trigger with TTL capability. This means lighting quick recycle times, TTL capability, and all the benefits of fiber optic cables (e.g., flood proofing). 

We were able to test the Olympus, Nikon, and Sony SMART TTL triggers. There is also one available for Canon. Overall the triggers worked excellent. The Olympus and Nikon triggers both worked seemlessly. The Sony trigger worked well, but we did find that it could overexpose the scene a tad when paired with the Sea & Sea YS-D2J. Theoretically you could compensate for this by adjusting your EV on the strobe or in camera.


Turtle TTL Converter - Retail Price and Where to Buy

The retail price of of a Turtle SMART TTL trigger ranges from $429.99 to $499.99. We think this price point is well worth the benefits of automatic strobe exposures and quick recycle times. All Turtle SMART TTL triggers are available for sale at Bluewater Photo.

Click here to purchase a Turtle SMART TTL trigger


Setting Up Your Turtle SMART TTL Trigger

When you first purchase your Turtle, it's absolutely essential that you program your TTL trigger for your camera and strobe. It's easier than it sounds. First you download a loader from the TRT-electronics FAQ page. Then you open the software and select your strobe that you will be using with your camera. 




Mark Hatter Puts the Turtle SMART TTL Trigger to the Test

Decoding TTL

A frequent question I’m asked while teaching underwater photography is; can I use my camera’s TTL mode with my strobes?  It’s at the same time a great question and a loaded question.

TTL means “Through The Lens” metering for flash control.  ”TTL metering" means that the light is measured from behind the lens to determine the correct shutter and flash settings.  Camera manufactures offering flash units (which they make), pair them via proprietary firmware, specifically for their camera systems.  This makes sense, as Canon, Nikon and others want you to buy their flash units. These camera makers “match” their flash units so that they “talk” to each other giving the shooter perfect TTL metering and exposure from shot to shot.

This works great for camera bodies with matching flash units but tends to fall short when trying to employ a third party flash with the Original Equipment Manufacturer (OEM) camera body.  In other words, strobes (flash units) we employ for underwater (UW) photography, manufactured by third party sources, do not have access to the proprietary firmware developed by the camera OEM.  Consequently, the UW strobe cannot effectively talk to the camera enabling accurate TTL exposure. 

This said, there are third party manufacturers that do make so-called TTL converters, which attempt to decode the OEM firmware algorithms.  In doing so, their products are designed to “translate” as best they can the OEM’s TTL metering algorithm, “converting” it into a language understood by the strobe.

I have owned more than one of these types of converter units over the years and have not been able to achieve repeatable, reliable and accurate TTL metering results shot to shot with my UW kit.

So I abandoned the search for a TTL converter and preached the merits of shooting in full manual mode for both camera and strobes.  My philosophy has been, I can do a better job of making lighting decisions than the camera can in an UW environment.  “Take the decision making process away from the camera and make the light control decisions yourself,” I have been telling my students.

But the question of whether TTL can be useful in UW photography continues to be raised and, perhaps it’s time to re-evaluate the merits of a TTL device, especially since I own one, if simply employed as a manual trigger device for my strobes. 

Unlocking TTL

I shoot a Nikon D850, which does not have a built in flash unit.  It requires a third party “flash trigger” fixed to the hot shoe of the camera body, inside the housing, to initiate a strobe to fire.  I shoot Subal housings, which are space limited in the housing’s “dog house” where the flash trigger is deployed.  Consequently, the TR TTL Electronics Smart Turtle is the recommended flash trigger, by Subal, to use with my D850. 

Ironically, as I have been preaching manual shooting for years, I have completely ignored the TTL function of my Smart Turtle, until now....

So I downloaded the specifically designed firmware for the Nikon D850 and Inon Z240 strobe (they have different firmware loads for different cameras bodies and strobes) from the Smart Turtle website, into my Smart Turtle.

Being restricted from travel, like the rest of the world during the current pandemic, I happily grabbed a couple of my grandson’s toys and jumped into the pool to put my Smart Turtle to the test with my105mm macro and a pair of Inon Z240 strobes.

Before I reveal the results, I have to say that the Smart Turtle is a real powerhouse packing plenty of energy, enough to fire a pair of strobes via fiber optic cables, for at least two dive’s worth of shooting.  Recharging is super-fast using a USB cable provided with the unit.  My charged Smart Turtle can outlast the batteries in my Inon strobes.  

Macro, 105mm, Coleman Shrimp. f-22, ISO 400, 1_250 sec Smart Trutle Manual Mode


It's time to test  

The Distance Test

First, I reset my D850 from “manual” to “TTL,” full power,” in the flash menu.  Next, I set my ISO to 400, aperture to f-22 and shutter speed to 1/100 second.  I set metering and focus points to “spot.” 

Next, I set my Inon strobes to “i-TTL” and ensured that the “TTL pre-flash suppression button” on the back of the strobe was set “off,” allowing any pre-flash needed for TTL metering to occur.  

I then set a test run of shots beginning at 3 feet from the subject, moving all the way up to close focus.  Between shots I reviewed both the camera’s histogram and the LCD for results.  

Much to my surprise, the shots were nearly perfect!  The histograms were well balanced with no clipping and, looked similar at every distance.

Unprocessed RAW f-22, ISO 400, 1_100 sec ~36 inches


Unprocessed RAW f-22, ISO 400, 1_100 sec ~ 18 inches



With the ability to achieve TTL it appears that, at least for my D850, Inon Z240 strobe and Smart Turtle combination, the little flash trigger/converter accurately translates strobe duration to produce a perfect TTL exposure from the point where light fall-off occurs from the strobe just due to maximum distance, all the way up to close focus.

I was concerned about trigger delay, which could be an issue shooting in the TTL mode as pre-flash is occurring, just before the shutter is released, but apparently with the camera set in the manual mode, the camera shutter triggers immediately, as you would expect.  In short, no trigger delay.


Pushing TTL to the Extremes

I continued to test using different shutter speeds, different apertures and different ISOs.  I was able break from perfect TTL exposures at extreme settings, e.g. aperture set at higher than f-25 with shutter speeds above 1/200 second or, an aperture at f-5.6 and shutter speed slower that 1/60 of a second.  But the “sweet spot” shooting around my initial settings was spot on.


Unprocessed RAW f-5.6, ISO 400, 1/25 sec @ ~10 inches

Unprocessed RAW f-22, ISO 400, 1/250 sec @ ~10 inches

TTL with A, S, and P Modes

The only other time I could break from a solid TTL performance was when I set the camera to Aperture Mode, Shutter Speed Mode or Program Mode (which produced the worst exposure).  Clearly, manually setting aperture, shutter speed and ISO is the right combination of settings with the system I was testing. 


Speed Test

For a final test, I reentered my camera’s menu and set the flash setting to “TTL, 1/27th power” to attempt rapid fire shooting at 7 frames per second (fps).  Since the strobe would not have sufficient time to recharge between shots, I set my ISO to 2500, aperture to f-22 and shutter speed to1/160 and shot at near close focus range, figuring the strobes might be able to keep up.  And they did!  So did the TTL!  While not perfect, I was able to achieve 3-4 shots as fast as I could pull the trigger.   TTL was validated once again on the camera’s histogram and LCD image.

Unprocessed RAW TTL 1/27 power, 7fps, ISO 2500, f-22, 1_160 sec, rapid sequence image #1


Unprocessed RAW TTL 1/27 power, 7fps, ISO 2500, f-22, 1_160 sec, rapid sequence image #2






So now I’m left with a dilemma. 

At least for my D850/Inon Z240/Smart Turtle system, I can achieve excellent TTL results, and I cannot wait to get back into the water to test my system out on a reefscape in Bonaire.

This is an unexpected, positive discovery which, I believe, will shape the way I shoot going forward. If I can achieve perfect TTL without having to manage camera settings or strobe distances from shot to shot, why would I not want to shoot that way going forward?  And it leaves me to ponder…What am I going to say to the next student who asks whether shooters can employ TTL for UW photography?





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