Knowledge Base

Problem

A user wants to know whether the Dynamic Subtraction detection method resets the background reference for each new video file when using the 'Track all saved video files' option, particularly when videos were recorded under different lighting conditions.

Details

When EthoVision uses Dynamic Subtraction, the background reference updates incrementally during tracking to account for small environmental changes (e.g., bedding displacement, water surface movement). However, it does not fully reset to a new background between videos in a batch — it starts from the same captured background defined in Arena Settings. This is relevant when video files were recorded under different conditions (e.g., different lighting, different times of day). Affected versions: EthoVision XT (multiple versions).

Solution

1. Dynamic Subtraction updates the background reference during acquisition but does not perform a full reset between videos in a batch — it always starts from the background captured in Arena Settings.
2. It is suitable for handling minor changes within a session (e.g., bedding movement, water ripples) but not for significant lighting differences between videos.
3. If your videos were recorded under meaningfully different conditions (e.g., different lighting levels, different times of day), create separate experiments or arena configurations, each with a background image captured under the matching conditions.
4. For each group of videos with similar conditions, grab a fresh background in Arena Settings that matches those videos before tracking.
5. If small background drift is expected within a session, Dynamic Subtraction is appropriate and no additional steps are required.