■Visibility and Backscatter

Many small particles such as plankton (marine snow), fine sand, and silt are suspended in the water.
When illuminated by a strobe or flash, these particles reflect light back toward the camera and appear as bright spots in the image.
This phenomenon is called backscatter.

To reduce backscatter:

• Choose dive sites with good visibility and fewer suspended particles.
• Avoid disturbing sand or silt with your fins.
• Approach the subject closely to reduce the amount of water between the camera and the subject.

Backscatter

When using a built-in flash on a compact digital camera, the light is emitted straight ahead from near the lens. This direct lighting increases the likelihood of backscatter.

Straight flash angle increases backscatter

Backscatter can be greatly reduced by using an external strobe positioned away from the camera and angled slightly outward.
Angled lighting minimizes the reflection of particles directly back into the lens.

External strobe angled outward