Knowledge Base

Problem

Light reflected off the water surface in a water maze creates bright specular highlights or glare spots in the camera image, causing EthoVision to misidentify the reflections as the tracked animal or otherwise disrupting detection.

Details

This is an environmental/laboratory setup issue rather than a software configuration issue. Specular reflections from overhead or ambient lighting on the water surface introduce false high-contrast regions that EthoVision's detection algorithm can pick up as subjects. The problem is particularly severe with point-source overhead lights or when lighting angle produces direct reflections toward the camera.

Solution

1. **Eliminate or diffuse the light source causing reflection**: Replace point-source overhead lights with diffused lighting panels or softboxes to produce uniform, glare-free illumination.
2. **Adjust the angle of lighting**: Position lights at an oblique angle relative to the camera axis to redirect reflections away from the camera's line of sight.
3. **Use polarizing filters**: Attach a circular polarizing filter to the camera lens to reduce specular reflections from the water surface.
4. **Add a light-diffusing covering**: Some labs stretch a diffusing material (e.g., tracing paper or diffusion film) above the maze to soften direct light before it reaches the water surface.
5. **Stabilize lighting**: Ensure lighting is constant and free of flicker, as changing reflections are more likely to be detected as moving objects.
6. **Adjust EthoVision detection settings** as a secondary measure: Refine the brightness/contrast thresholds in Detection Settings to better distinguish the animal from the background. Ensure a clean background reference image is captured under the corrected lighting conditions.
7. Note: Stable, reflection-free lighting is a fundamental hardware requirement for reliable EthoVision tracking. Software-only workarounds cannot fully compensate for severe optical artifacts from water reflections.