When I first entered the frigid waters of Whidbey Island in Washington, with the Sony a6400 in hand, I had a simple yet ambitious goal—to capture high-quality 4K underwater video. Although I don’t consider myself an expert in videography, the promise of the Sony a6400’s capabilities drew me in. I was curious to see how it would perform in real-life underwater scenarios, and it did not disappoint.
The Journey Behind the Footage
The footage featured in the video was captured across seven dives in the Pacific Northwest, during a period of remarkably calm tidal conditions. These favorable tides granted me access to some of the region’s most treasured dive sites—locations usually inaccessible due to the strength of the currents, which can reach up to 14 knots. The currents are vital to sustaining the nutrient-rich waters that feed the spectacular invertebrate life of the Puget Sound. However, diving here requires precise timing; shore dives must be executed during slack tide to avoid dangerous drift and poor shooting conditions.
Many of the video’s standout clips display immense walls blanketed in vibrant invertebrates, particularly various species of anemones. These locations around Whidbey Island were among the most exciting to film. Using my Venom 60 RGB video light and Symbiosis SS2 strobe, I focused on bringing out as much color and texture as possible. Navigating strong currents required careful control of movement and lighting. A steady pan or a well-anchored stance became essential for achieving cinematic shots with dynamic shadows.
Meeting the Wolf Eels
Early in the video, you’ll notice several wolf eels making an appearance. In the Tacoma area, there are dive sites well-known to local divers for hosting particularly sociable wolf eels. Much like curious cats, they cautiously observe divers but sometimes come out for a closer look. That day, both a sub-adult orangish female and a larger gray male made appearances. The male was seen retreating into his den, likely to reunite with his mate. Their behavior added personality and movement to the footage, providing rare moments of connection between marine life and the camera.
The Challenge of Macro Video
The most difficult yet rewarding part of this filming experience was capturing the macro footage. The Sony a6400 excels in video detail, and this is particularly evident in the clips focusing on sculpin eyes and octopus skin. Although achieving autofocus in macro mode was more challenging, the results were worth the effort. One memorable sequence includes a small red octopus crawling across a muddy slope during a night dive with almost no visibility. Even under such difficult conditions, I was able to capture sharp, expressive footage that highlighted the strength of the a6400’s video capabilities.
In the following parts, we’ll explore the technical performance of the Sony a6400 underwater, including video quality, ergonomics, lighting gear used, and how it compares to other popular cameras like the Panasonic GH5.
Compact Build, Impressive Ergonomics
Shooting underwater requires equipment that is both durable and easy to handle, especially in demanding dive environments. The Sony a6400 strikes an ideal balance between size and functionality. Smaller than most mirrorless cameras, yet packing an APS-C sensor, the a6400 is perfect for divers needing agility. Its lightweight design allowed me to navigate tight corners and swim against currents without quickly tiring. The streamlined form also meant I could easily stabilize the rig against rocks or coral outcrops when capturing macro footage.
With any compatible underwater housing, the camera’s buttons are easily accessible. Most housings provide direct access to the record button, allowing users to capture video on the fly. This instant control is crucial in spontaneous situations, such as when marine life suddenly appears. However, pressing the record button directly initiates manual video mode, requiring you to adjust exposure settings manually. Alternatively, turning the mode dial to video mode gives full control with options such as shutter priority, aperture priority, program mode, and manual.
During my dives, water clarity, lighting, and current conditions were unpredictable, so I opted to shoot primarily in program and aperture priority modes. The metering system on the Sony a6400 handled shifting lighting well. Even in dim environments, like shadowy wall crevices or late-afternoon dives, I rarely encountered exposure problems. The intuitive layout of the camera’s settings ensured I could make adjustments swiftly without missing critical moments.
Video Resolution and Oversampling Power
Where the a6400 truly excels is in its video resolution and detail. It records 4K video by oversampling from a 6K image using the full sensor readout. This means every pixel is utilized, which drastically improves clarity. Unlike many cameras that rely on pixel binning or cropping to achieve 4K footage, the a6400’s method results in footage that’s exceptionally sharp, nuanced, and lifelike. The richness of detail is especially noticeable when observing the fine textures of anemones, rockfish scales, or octopus skin.
In comparison to many full-frame cameras, this level of detail from an APS-C sensor is impressive. For example, the Canon EOS R, although full-frame, performs a significant crop during 4K recording, effectively reducing the field of view and sometimes diminishing sharpness. The a6400, meanwhile, avoids that limitation, preserving both angle and quality. The result is cinematic footage that doesn’t require excessive enhancement in post-production.
Another impressive aspect of the a6400’s video quality is its dynamic range. I could recover details from shadows without introducing significant noise and preserve highlight details during high-contrast lighting situations. Whether I was shooting brightly lit anemone gardens or shadowed rock overhangs, the footage retained a balanced exposure. This made the editing process more efficient, allowing me to focus on color grading and fine-tuning rather than correcting technical issues.
Color Accuracy and White Balance Control
Historically, Sony struggled with color accuracy in their JPEG and video outputs, especially when compared to Canon and Nikon. However, with the a6400, Sony significantly improved its color science. The colors captured underwater were vibrant, natural, and closely aligned with reality. Most scenes required minimal grading, and when they did, the changes were subtle.
The built-in white balance options were more than capable of adjusting to the shifting blues and greens of the Pacific Northwest. During deep dives, I set a custom white balance to compensate for the ambient light loss at depth, which resulted in truer reds and oranges. The footage of the wolf eels and sculpins, in particular, benefited from this control. Their natural coloration, often muted by water conditions, remained visible and striking in the final cut.
Even though some scenes, such as those in low light or with fast-moving subjects, required correction during post, the overall improvement in rendering made those edits straightforward. The video clips did not suffer from aggressive compression or awkward tinting, as I’ve sometimes experienced with earlier Sony models.
Autofocus Capabilities
Autofocus plays a crucial role in underwater video. Subjects may move suddenly, visibility can shift rapidly, and the camera must respond in real-time to these changes. Fortunately, the a6400 boasts Sony’s acclaimed real-time autofocus system, which tracks subjects with speed and precision. I was particularly impressed by how quickly the camera locked onto moving marine life, from darting rockfish to slow-moving nudibranchs.
The new animal eye autofocus feature worked surprisingly well underwater, even though it’s primarily designed for terrestrial wildlife. During macro filming of an octopus, the eye detection maintained focus despite the creature’s constant motion and changing position. This added an organic, responsive touch to the footage that manual focus alone could not achieve.
For wide shots, the autofocus had no trouble tracking schools of fish or individual animals as they swam across the frame. In macro shots, the Sony 50mm f/2.8 macro lens did face occasional hesitation. At times, it searched back and forth for focus, especially when shooting subjects that were small and moved irregularly. This was evident in the final clip of the octopus, where slight focus hunting can be seen. Despite this, I was still able to salvage excellent footage with patience and manual override where needed.
Image Stabilization and Rolling Shutter
One area where the a6400 shows its limitations is image stabilization. Unlike the Sony a6500 or Panasonic GH5, it lacks in-body stabilization. This means any stabilization must come from the lens or the housing setup. In calm water or with a solid anchoring technique, this isn’t a major issue. However, in surge conditions or when panning, the footage can become slightly shaky.
To mitigate this, I used slow, controlled movements and tried to stabilize the camera on rocks or sandbeds. During post-production, I applied stabilization filters where necessary. Though this added time to the editing process, the result was a smooth, professional-looking video.
Rolling shutter can also be a concern, especially when panning rapidly. The camera’s sensor takes time to read each frame, so vertical lines can appear skewed if the camera or subject moves too quickly. This was noticeable when filming fast-moving wolf eels or sweeping along colorful reef walls. The solution was to slow down and maintain consistent motion. For seasoned underwater videographers, this isn’t a major hurdle, but beginners may find it challenging.
Underwater Lighting with the Sony a6400
Lighting is essential for high-quality underwater video. The deeper you go, the more color is lost, especially reds and yellows. For this project, I used two primary light sources: the iTorch Venom 60 RGB video light and the iDiveSite Symbiosis SS-2 strobe and video light.
The Venom 60, with its 6000-lumen output, gave me full confidence when lighting wide-angle scenes. Its adjustable beam and light modes allowed me to tailor brightness levels based on subject distance and water clarity. Even with just one light, I was able to fill most scenes evenly without creating harsh shadows. For macro work, I paired the SS-2 strobe with its integrated video light. This combo made it easy to switch between stills and video, especially when encountering rare or skittish creatures.
For most dives, this two-light setup offered versatility and control. The lightweight build and efficient battery life meant I could complete long dives without concern. Other lighting options exist, but this setup offered a practical balance between power, portability, and ease of use.
Equipment and Lens Selection
I used a mix of lenses to adapt to different subjects and shooting conditions:
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The Sony 16–50mm kit lens with the Fantasea UWL-09F wet wide-angle lens was perfect for wide reef scenes and general use.
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The Sony 10–18mm lens gave me broader fields of view, useful for large subjects like wolf eels and sea walls.
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The Sony 50mm f/2.8 macro lens allowed detailed close-ups of nudibranchs, sculpins, and octopuses.
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I occasionally used a Bluewater +7 macro diopter for extra magnification.
This combination of lenses ensured I could switch between filming styles without compromising video quality. Each lens performed well when paired with the camera’s autofocus and exposure settings.
Comparing the Sony a6400 and Panasonic GH5
In recent years, the Panasonic GH5 has been hailed as a top-tier camera for underwater video. Its 4K @ 60fps capability, in-body stabilization, and pro-level controls have earned it a loyal following. However, the Sony a6400 has emerged as a strong competitor, offering distinct advantages.
Advantages of the Sony a6400
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Superior Detail: Thanks to the 6K oversampling and full sensor readout, the a6400 delivers unmatched sharpness and detail in its price range.
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Better Autofocus: Real-time tracking and animal eye detection outclass the GH5’s autofocus, particularly in challenging environments.
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Improved Color Rendering: Sony’s updated color science puts it closer to Canon and Panasonic in terms of accuracy and vibrance.
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Lower Noise: In low-light conditions, the a6400 exhibits less noise compared to the GH5, thanks to its APS-C sensor and newer processor.
Advantages of the Panasonic GH5
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In-Body Stabilization: Ideal for shooting in surge or while moving, the GH5’s stabilization allows smoother footage directly from the camera.
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Higher Frame Rate: The GH5 supports 4K at 60fps, useful for slow-motion footage or fast action.
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More Video Tools: The GH5 offers pro-level video features, including better customization of frame rates, bitrates, and video profiles.
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Better Rolling Shutter Performance: The GH5 has less distortion when panning quickly or filming fast-moving subjects.
Verdict
Choosing between these two cameras depends on your needs. If stabilization and higher frame rates are critical—especially for filming fast subjects like fish schools—the GH5 may be a better fit. However, if image quality, autofocus precision, and compact design are your top priorities, the a6400 is a clear winner. For macro and close-up filming, especially in calm waters, the Sony a6400 shines with its detail and color fidelity. Experienced videographers will appreciate the richness of footage it delivers.
External Monitor Compatibility and Log Profiles
As underwater videographers push the boundaries of quality and control, external monitors and log profiles become increasingly valuable. Fortunately, the Sony a6400 provides solid support in both areas, making it a serious contender for more advanced work.
The camera is compatible with external monitors via a mini HDMI output. While not full-size HDMI like the Panasonic GH5, it still allows for real-time monitoring on larger screens—ideal when working in more complex underwater environments or when filming professionally. Monitoring footage live on a larger screen can make a huge difference in verifying sharp focus, correct exposure, and framing—especially when natural visibility is poor or lighting conditions are inconsistent.
The a6400 also offers several picture profiles for filmmakers, including S-Log2, S-Log3, and Hybrid Log Gamma (HLG). These profiles provide greater flexibility in post-production for color grading and tone mapping. While shooting in log requires more effort during editing, it’s worth it for those looking to create cinematic footage with accurate highlights and shadows. During my dives, I didn’t rely heavily on log profiles due to the already excellent out-of-camera color. However, for future projects requiring tighter control of contrast and saturation, this will be an invaluable tool.
RAW Video and Limitations
One of the few missing features on the a6400 is the ability to record RAW video internally or externally. This may be a dealbreaker for professional cinematographers seeking the most flexibility in post-production. For those users, alternatives like the Nikon Z6, which supports external RAW recording with certain devices, may be more suitable.
That said, the a6400’s codec and bitrates are still strong enough for most underwater video use cases. The image detail retained during 4K oversampled recording holds up well during post-processing, including color grading and sharpening. For divers who are not producing commercial-grade content, the lack of RAW video is not a significant limitation.
Audio Recording Underwater
Although not emphasized in underwater videography, audio can play a role in certain projects. The Sony a6400 has a built-in microphone as well as a 3.5mm microphone jack for external mics. However, recording clean audio underwater is rarely practical due to ambient noise and housing limitations. For most projects, you’ll want to add ambient or musical audio in post.
If you're creating documentary-style pieces or above-water segments (e.g., gear reviews, dive briefings), attaching an external mic above the surface works well. Housing manufacturers sometimes offer accessories or workarounds to isolate or enhance audio input, but most underwater filmmakers prioritize visuals over in-dive sound.
Field Reliability and Battery Life
Battery life underwater is a make-or-break factor. Fortunately, the Sony a6400 delivers acceptable performance in this regard. During my dives, one fully charged battery typically lasted a full dive session (about 60–75 minutes of intermittent recording). I carried two spares in a dry case on the boat to ensure uninterrupted operation between dives. While not groundbreaking, the power management is efficient for a camera of this size and performance class.
Additionally, the build quality proved resilient against condensation and pressure when paired with a proper housing. Even in the cold waters of the Pacific Northwest, I experienced no overheating or freeze-ups. For divers planning remote trips or extended shoot days, investing in high-quality batteries and charger systems is highly recommended.
Portability for Travel Divers
If you travel frequently for dive trips, weight and portability are key considerations. The Sony a6400 excels in this area. Its compact form factor makes it an ideal travel companion, and the ability to pack both wide and macro lens options without excessive gear is a major benefit. I was able to carry my entire rig—including housing, lighting, and spare parts—in a single carry-on-sized backpack. This is nearly impossible with a full-frame DSLR or cinema camera setup.
It’s worth noting that some airlines may request hand inspection of lithium-ion batteries or underwater lighting gear, especially strobes and high-output video lights. Be prepared with documentation and safe transport bags to avoid issues at airport security.
Conclusion:
After completing seven dives, facing conditions that ranged from poor visibility to strong surge, and filming everything from macro octopuses to towering anemone walls, I can confidently say the Sony a6400 is one of the most versatile, compact, and capable underwater video cameras on the market today.
Its biggest strength lies in the oversampled 4K video, which provides rich detail far beyond what you’d expect from a camera this size. The autofocus system is nearly flawless in wide-angle use and surprisingly functional in macro scenes. The color rendering has come a long way, delivering realistic and vibrant tones without aggressive grading. Even without in-body stabilization, careful technique and post-processing make up for this shortfall in most use cases.
For beginner to intermediate videographers, the Sony a6400 is a powerful gateway into professional-level underwater video. Its intuitive controls, strong battery life, and excellent image quality make it a joy to use. For seasoned professionals, it offers a lightweight, secondary rig that doesn’t sacrifice quality, perfect for travel or casual shoots.
The limitations—such as no in-body stabilization, mini HDMI instead of full HDMI, and the absence of RAW video—are all manageable when weighed against the a6400’s advantages. Add to that the wide availability of housing and lens options, and you have a system that can adapt to nearly any underwater filming scenario.
Whether you’re filming in cold, nutrient-rich waters like those of the Pacific Northwest or exploring coral reefs in the tropics, the Sony a6400 delivers performance that rivals more expensive, bulkier systems. It has earned a place in my gear bag—and more importantly, in my creative process.
If you're looking to take the next step in your underwater filmmaking journey and want a reliable, high-quality, and travel-friendly setup, the Sony a6400 deserves your serious consideration.