Underwater imaging
ROV lighting: reducing backscatter before adding more lumens
More light can brighten suspended particles as well as the inspection target. A useful ROV lighting specification combines camera-to-target distance, light placement, beam coverage and dimming, rather than selecting on lumens alone.
Define what the operator must see
Write the visual task in concrete terms: reading a marking, identifying a connector, observing marine growth or documenting a surface. State the target size, expected working distance and whether the image is for navigation or detailed inspection. A wide navigation view and a close inspection view may need different illumination settings.
For example, 'read a sample identification plate at 0.5 m in representative site water' is a testable brief. It is an illustrative target, not a visibility claim for any camera or light. Keep a sample plate or other repeatable target so alternative layouts can be compared consistently.
Move the light away from the camera axis
Backscatter is light returned to the camera by particles in the water. Reducing illumination of the water immediately in front of the lens can improve the view. Blue Robotics' assembly guidance describes placing lights outside the frame to reduce backscatter, while noting the reduced mechanical protection.
On a custom frame, make spacing and aiming adjustable during development. Aim to illuminate the target without concentrating both beams directly in front of the lens. Check the camera's full tilt range, shadows from the frame and any manipulator entering the scene. There is no universal mounting separation that works for every beam and water condition.
Dimming and beam coverage matter
Start an in-water comparison at a low brightness and increase it while watching target detail, particle glare and bright-surface saturation. Keep camera settings consistent where possible. Otherwise, an automatic exposure change can obscure the effect of moving or dimming a light.
Check beam coverage at the intended working distance, including the edges of the camera view. An illuminated centre with dark corners may be acceptable for a narrow inspection target but poor for piloting. Trial one light, then the intended pair or array, rather than assuming multiple beams always improve the result.
A Blu-Sub electrical example
Blu-Sub lists its 1500-lumen dimmable light with a 10–28 V input, 17 W maximum power, approximately 90-degree beam and PWM dimming. The documented PWM level is 3.3–5 V with a 1100–1900 microsecond control range. Confirm the supplied revision and wiring documentation before connection.
As a simple load estimate, two 17 W lights total 34 W at maximum specified power. At a 24 V supply that is about 1.42 A, calculated as 34 / 24, before allowing for the rest of the system and distribution losses. This electrical calculation does not predict underwater viewing distance.
The manufacturer specifies a shared ground between the light supply and PWM source. Include power, signal and cable routing in the installation drawing, then confirm that the selected controller output can provide the required signal. Check cable termination and the assembled system's depth suitability separately from the optical trial.
Use a repeatable in-water comparison
Place the same target at marked distances. Record the light spacing, aim, brightness command, camera exposure and water conditions for each clip. Change one factor at a time. Compare whether the task is achievable, not simply which recording looks brightest.
Repeat the best layout with the camera tilted and with representative nearby reflective surfaces. Where practical, assess image quality during controlled vehicle movement as well as while stationary. Retain an example of the required image quality with the project specification so acceptance does not depend on memory.
Prepare a lighting enquiry for your ROV
Send the camera model, target and working distance, water conditions, available mounting space, supply voltage, control interface and required operating depth. A photo or sketch of the front of the vehicle is particularly useful for discussing shadows and adjustment space.
Browse subsea lighting and underwater cameras together. The objective is a usable inspection image from the assembled system, so reserve time for an in-water trial before fixing the mounting design.
Sources & basis
What this is based on.
- Blue Robotics: light placement and the protection/backscatter trade-off. This is a mounting principle, not a claim of cross-brand compatibility.
- Blu-Sub: dimmable underwater LED light specifications and control wiring.
- The two-light power calculation and proposed comparison procedure are illustrative; no field visibility or depth-test result is claimed.
Published 5 September 2026. Last revised 5 September 2026. Corrections to sales@
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