Knowledge Base

Problem

EthoVision fails to reliably detect or track white or light-colored animals (e.g., white mice, white rats) when the arena background, bedding, or apparatus is also light-colored or reflective (e.g., silver thermal plates, light bedding). The software picks up artifacts, loses the animal, or gets 'stuck' on a fixed point.

Details

Affects EthoVision XT users tracking albino or white-coated animals in arenas with low contrast between subject and background. Common scenarios include white mice on light bedding, white rats in thermal place preference chambers with silver plates, and animals in arenas with visible shadows or reflections. Both static and dynamic subtraction methods may struggle. IR illumination setups can also cause unexpected contrast inversions depending on bedding material. Artifacts, false detections, and tracking loss are the primary symptoms.

Solution

1. Maximize contrast between subject and background:
- Use dark, non-reflective bedding or arena flooring to contrast against white animals. Avoid light gray, beige, or silver surfaces.
- For thermal place preference chambers with silver plates: consider placing a thin dark, heat-conductive material over the plates if experimentally permissible, or test whether darkening surrounding walls improves detection.
2. Optimize lighting:
- Use bright, even, diffuse illumination to minimize shadows. Shadows in the arena create false contrast gradients that confuse detection.
- Fluorescent lighting is preferred over incandescent or halogen, as the latter emit infrared and can degrade IR camera performance.
- Cover windows to prevent variable ambient light.
3. If using IR illumination:
- Test dark bedding materials under IR illumination — some materials that appear dark under visible light appear white under IR, reducing contrast.
- Switch visible lights off and on to determine whether they are contributing IR interference.
4. Consider switching subtraction method:
- If using Static subtraction and visible lights are adding infrared, the arena floor may be detected instead of the animal. Try Dynamic subtraction to account for gradual background changes.
5. Adjust detection settings:
- In Detection Settings, use the Threshold slider and preview to isolate the animal pixel blob from the background. The animal should appear as a solid, distinct blob.
- Use the 'Minimum object size' filter to exclude small artifacts.
6. For animals that are lost and then re-found at an incorrect location ('stuck' tracking): enable 'Maximum velocity' limits or use the Track Editor to manually correct lost segments post-acquisition.
7. See also: 'Tracking Animals with Poor Contrast Against Background' and 'Camera Image Dark or Not Displaying During Acquisition – IR Illumination and Camera Setup'.