The TTL Debate: Why We Still Choose Manual (And When You Shouldn’t)

In the world of underwater photography, the initials TTL—which stand for "Through-The-Lens"—refer to the camera’s ability to control your strobe output automatically, judging the flash exposure through the lens. While it sounds like a dream for simplifying your photography, as soon as you truly want to nail your pictures in camera, like we (Alex Mustard and Matthew Sullivan) do, it is just faster and easier not to use it.

How TTL Works: The Pre-Flash Dance

Underwater, TTL doesn't actually happen during the exposure. Instead, it happens in a split second before the shutter fully opens, so fast we photographers cannot discern it:

1. The Pre-Flash: The camera triggers a weak "test" flash from your strobes.

2. The Measurement: The camera’s sensor looks through the lens to see how much light is reflected back from the subject.

3. The Calculation: It calculates the exact power needed and sends a second signal.

4. The Main Flash: Microseconds later, the strobe fires the "correct" amount of power for the final image.

To make this work, you generally need two things: a TTL-enabled strobe and a specific TTL flash trigger board inside your housing to translate the camera’s signal.

Why We Don’t Routinely Use TTL

Despite how advanced the technology has become, like most experienced photographers we don't personally use it for our daily work. This is because we are more interested in the quality of light and creative vision than whether a strobe can guess the exposure.

The biggest flaw is that TTL is an "estimation" and when it gets it wrong you need to correct it with exposure compensation. However, for the next shot it might guess right, but the result is wrong because of the compensation you dialed in! Furthermore, TTL is good with simple scenes, but as compositions and lighting become more artistically interesting, the TTL will struggle more. So ultimately it holds your photography back.

• Dual Strobe Logic: Most underwater TTL systems don’t actually know there are two strobes attached, so they send the same start and stop instructions to both strobes. This works if your subject is dead-center, but if you move the subject to one side for a better composition, one side will be overexposed and the other underexposed.

• The "Moving Target" Problem: It is possible to use compensation to fix a TTL error, including balancing the light between two strobes. However, because TTL is always based on the previous guess, the effect is unpredictable. It is much simpler to just set the strobes to a manual power and adjust consistently.

• Creative Stagnation: Because TTL works best for centered, front-lit subjects, photographers who use TTL often find themselves subconsciously only taking the "safe" compositions where TTL works.

When We Do Recommend TTL

We want to be clear that we aren't anti-TTL on principle; it is a fantastic tool in specific situations:

• Building Confidence: If you are new to underwater photography, TTL is a great way to build confidence. It lets you focus on your diving, buoyancy, and composition without being overwhelmed by technical settings.

• Field Guide/Basic Shots: If your goal is simply to document what you see (like a fish ID guide) with standard front-lit macro or wide-angle, TTL works perfectly fine.

• Challenging Conditions: In some environments—like diving with thick gloves in cold water—fiddling with small strobe dials can be a massive pain. In those cases, the convenience of TTL can outweigh the need for manual precision.

How TTL Can Limit Your Creative Vision

One of the most significant drawbacks of relying on TTL is how it subtly dictates your photography. As we often see in image reviews, we can almost always tell when a photographer is shooting TTL just by looking at their compositions.

Because TTL is an automated system, it has a "comfort zone" where it performs best. This leads to a phenomenon where the technology, rather than the photographer, begins to drive the creative process.

The "Safe Shot" Trap

TTL works most reliably under very specific conditions:

• Standard Macro: Front-lit subjects that are fully in the frame.

• Central Wide-Angle: Large subjects placed directly in the center of the picture.

Photographers who use TTL quickly realize—subconsciously or otherwise—that these are the shots that "work". Consequently, they tend to repeat these same two types of compositions over and over again. Their portfolios often end up looking very similar, with the only real difference being the species of fish in the frame.

Discouraging Innovation

The moment you try to step outside of those "safe" compositions, TTL typically struggles or fails. This often discourages photographers from trying more advanced techniques:

• Selective Lighting: If you want to use a snoot for selective macro lighting, TTL often produces poor results.

• Backlighting: Creative backlighting is another area where TTL logic often falls apart.

• Off-Center Composition: If you place a subject to the side of the frame to make the composition more interesting, TTL will frequently over-light the side closest to the strobe and under-light the far side.

Instead of learning how to adjust their lighting to fix these issues, many TTL users simply recompose so the technology works again. This creates a "glass ceiling" for your artistic progression. To truly care about the final product as an artistic endeavor, you need to take full control of your lighting.

The Case for Manual Exposure

The reason most of the world's top underwater photographers shoot manual isn't because they are trying to be "clever"; it’s because manual is actually easier.

Manual exposure is remarkably predictable. Underwater, we tend to take shots from the same distances and use similar settings for an entire dive. Once you dial in your power, you rarely have to move it more than a click or two. If a manual shot is wrong, you know exactly how to fix it for the next one.

Our Final Verdict: Use TTL to find your feet and build confidence. But as soon as you want to move beyond "standard" shots and start creating artistically interesting lighting, like backlighting or selective snooting, it’s time to switch to manual and take full control of your vision.

To view the original episode and hear the entire discussion, check out the video here: