Hi StereoLabs team and community,
I am working with multiple ZED 2i cameras for skeleton tracking (tracking distances between 2–10 m, testing one camera at a time under normal lighting conditions but for calibration I used a dark environment as advised). After evaluating five different units using the same procedure, I have observed some unexpected behaviour in both calibration and distance measurements. I would appreciate clarification before moving to the next stage of my experiments.
What I’ve observed
· As StereoLabs recommends, some cameras performed better with factory calibration (FC) compared to user calibration.
· However, for other units, user calibration sometimes resulted in better performance than FC.
These inconsistencies raised several questions:
My questions
1. Under what conditions does StereoLabs recommend performing user calibration instead of relying on factory calibration?
Are there specific indicators, symptoms, or accuracy thresholds that suggest a recalibration is necessary?
2. Can user calibration degrade performance if environmental conditions are suboptimal (e.g., poor lighting, monitor glare, low screen resolution, reflections)?
In other words, is the calibration process sensitive enough that suboptimal conditions may produce intrinsics worse than the factory defaults?
3. Does the ZED Calibration Tool provide a quality score, confidence measure, or any metric to help determine whether a calibration was successful or should be repeated?
4. Do calibration parameters drift over time, or should the factory calibration remain stable unless the camera experiences mechanical shock, temperature extremes, or physical damage?
5. What is the recommended robust procedure for user calibration?
The process appears susceptible to user-induced errors—particularly while moving the camera in front of the screen.
Is it preferable to minimize camera movement by mounting the camera during calibration?
Or is it acceptable to hand‑hold the camera and follow the on‑screen markers?
6. Do all calibration parameters (intrinsics, distortion coefficients, stereo baseline, etc.) contribute equally to the final calibration quality?
Or are certain parameters more critical for depth accuracy and downstream tasks such as skeleton tracking?
7. Across all five cameras tested, I observed systematic depth‑measurement biases: significant overestimation (6–14%) at approximately 2 m, improved accuracy between 4–8 m (typically <3% error), and increasing underestimation beyond 8 m. Could you explain the factors that may cause these distance‑dependent variations in measurement accuracy?
Any guidance or best practices would be greatly appreciated.
Thank you!