Perspective error occurs when positions, distances, or angles in a two-dimensional image differ from their true relationships in three-dimensional space. It is a central limitation of measurements made from a single camera view.
The error becomes more noticeable when the subject moves toward or away from the camera, the camera is not perpendicular to the plane of motion, or the movement occurs far from the calibrated area.
Ways to Reduce Perspective Error
- Position the camera perpendicular to the primary plane of motion
- Place the camera far enough away to reduce angular distortion, then zoom or crop as needed
- Keep the camera level, stable, and centered on the area of interest
- Perform calibration in the same plane as the movement being measured
- Use the same setup for comparison recordings
These practices improve consistency, but they do not turn 2D video into a complete three-dimensional measurement system. Results should be interpreted within the limits of the recording setup.