Does your smartphone's HDR actually work underwater? Technical analysis of what works, what fails, and why Night Mode is useless when diving.
Your smartphone's HDR and multiframe fusion behave differently underwater than on land. In shallow water with a still subject, HDR improves contrast. In deeper water, with movement, or with bubbles in frame, multiframe fusion produces artefacts. Night Mode is useless for diving.
It was 2023, at a site I know well off the coast of Cyprus. I had my Samsung Galaxy S23 Ultra in a Divevolk housing at 7 metres depth. A nice wall with groupers and amberjacks. I switched on automatic mode, shot, and looked at the result: the grouper in the foreground was doubled, with a ghostly halo around its fins. The HDR had tried to merge two exposures while the fish was swimming between them. Unusable image.
That day, I started systematically testing what smartphones actually do underwater, feature by feature, depth by depth.
Computational photography is the full set of software processing your smartphone applies before returning the final image: HDR, multiframe fusion, noise reduction, perspective correction, Smart HDR. These algorithms were designed for surface conditions: changing natural light, relatively stable subjects, standard distances of 0.5 to 10 metres. Underwater, almost all these assumptions fail at the same time.
Three factors complicate the lives of these algorithms when diving.
Your subject moves much faster than on land. A grouper, a ray, even coral in a slight current creates movement between two exposures.
You move too. Perfect neutral buoyancy does not exist at 100%, and every breath creates a few centimetres of displacement.
Suspended particles (plankton, sediment, air bubbles) create a textured background that disrupts the motion detection and autofocus algorithms.
HDR works correctly in two specific situations.
When you shoot towards the surface in backlight with a still subject in the foreground: a resting turtle, an anemone, a rocky bottom. The high contrast between a dark subject and the bright surface is exactly the problem HDR was designed to handle.
When you shoot in snorkelling or freediving conditions with a shallow, relatively stable subject. There, the merged exposure series can genuinely recover detail in surface highlights.
Beyond 10 metres, the scene becomes less contrasty because the warm wavelengths have already been absorbed by the water column. HDR has little dynamic range left to recover, and its processing introduces more problems than it solves.
The classic problem: two exposures merged over a subject that moved between them. You see ghosts around fins, tentacles, cilia. That is ghosting, and it is the main defect of HDR underwater.
My recommendation: disable automatic HDR as soon as you go below 8 metres or your subjects are in motion. Switch to RAW if your housing supports it.
Samsung Ocean Mode, available on the Galaxy S24 Ultra and S25 Ultra, deserves a separate mention. I have tested it since launch, and it is honestly the most intelligent computational photography feature designed specifically for underwater shooting.
What it does concretely: it automatically adjusts white balance to compensate for the absorption of warm wavelengths, slightly increases saturation in the reds and oranges lost at depth, and adapts exposure to low underwater light levels.
It is not aggressive multiframe processing. It is a camera profile adapted to the conditions. A much more sensible approach than forcing a generic algorithm into an environment it was never designed for.
What it does not do: replace colour correction in post-production for photos below 12 metres. Beyond that point, results remain flat and need a pass through Lightroom Mobile or an equivalent tool.
For a detailed comparative test of this mode, the article on Samsung Ocean Mode covers results across multiple dive sites.
Focus stacking (combining several photos with different focus points to maximise depth of field) is popular in terrestrial macro photography. Underwater with living subjects, it is nearly impossible. The octopus moved its arms. The nudibranch undulated slightly. The shrimp vanished between shots.
For underwater macro, it is better to choose the right aperture at the moment of shooting rather than hoping to compensate with stacking in post-production.
Night Mode accumulates light over a long duration (1 to 4 seconds depending on the model). Underwater, staying still for 4 seconds is nearly impossible. And fish do not cooperate.
Night Mode can produce something usable only on completely still subjects (coral, closed anemone, rock) in very calm and shallow water. That scenario represents perhaps 2% of real diving situations.
To recover light at depth, the approach remains the same: shoot wide open, raise ISO, correct in post. AI tools like Topaz DeNoise then recover the noise remarkably well, as detailed in the article on AI upscaling and denoising.
Here is what seven years of testing smartphones in housings have taught me.
RAW enabled: always. It is the only decision that leaves you options in post-production.
HDR: useful from 0-5m on still subjects with high contrast scenes. To be manually disabled at depth.
Night Mode: forget it for diving, except very specific edge cases.
Samsung Ocean Mode: the best underwater profile available in 2026, but not a replacement for post-production.
Multiframe fusion and Smart HDR: let the smartphone decide only if you have no access to manual controls, and correct in post.
Computational photography underwater is two generations behind the real needs of dive photographers. The best results still come from a good RAW file, a mastery of natural light, and AI tools like Topaz Photo AI in post-production.
If you work with a smartphone in a housing, the priority remains the same one I have always taught: RAW enabled, HDR controlled, trust your eye over the algorithm.
The question of AI-generated imagery and its impact on the authenticity of underwater photography is addressed in the companion article on marine deepfakes and generative AI.
AquaExposure receives no affiliate commissions on the smartphones, housings or software mentioned in this article.
Want to go further in mastering underwater photography technique? The AquaExposure underwater photography course covers shooting and post-production end to end, with practical exercises adapted to your equipment.
In shallow water (0-5m), HDR can improve contrast and recover surface highlights. In deeper water or with moving subjects, it frequently generates visible artefacts. Results vary considerably depending on the smartphone model.
Night Mode stacks multiple exposures over 1 to 4 seconds. Underwater, your subject moves, the water moves, and you move. The result is blurry or ghosted. It is only useful on completely still subjects in very calm shallow water, which is rare in real diving conditions.
No. In 2026, Ocean Mode is available on the Galaxy S24 Ultra and S25 Ultra. It optimises exposure and white balance for underwater conditions. The list of compatible models evolves with One UI updates.
For underwater photography, RAW is recommended whenever your housing allows it. It preserves more information for colour correction in post-production. The JPEG HDR processed by the smartphone can crush useful detail in the midtones.
Yes, this is the main problem. Bubbles, moving subjects and turbulence create blurry areas or double images in the fused frame. The more movement in the scene, the more visible and difficult to correct the artefacts become.
Aggressive HDR can artificially oversaturate blues and reduce the subtlety of water tones. AquaExposure recommends working from RAW with manual correction rather than relying on the smartphone's automatic HDR processing.
ProCamera allows you to disable HDR and shoot in RAW DNG. Halide also works on some compatible housings. Apple's native Camera app activates HDR automatically with no direct control option.
