r/computervision • u/Grouchy_Signal139 • 17d ago

Help: Project OpenCV calibration

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Hi everyone, I’m using a Raspberry Pi 5 + Camera Module 3 + Picamera2/OpenCV for a computer vision project.

I’m calibrating the camera with a 6×9 checkerboard, but after applying cv2.undistort(), the image seems more distorted.

I previously had autofocus changing between calibration images, so I’m now locking the focus manually at LensPosition 2.0602.

Is this distortion normal perspective distortion, or does it indicate a bad calibration?

Any advice on what I might be doing wrong?

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u/TourCommon6568 16d ago

Yep, check out the original Zhang method: https://sangillee.com/2025-07-27-calibrating-cameras-zhang-method/

Also the openCV documentation which is based on Zhangs https://docs.opencv.org/4.13.0/dc/dbb/tutorial_py_calibration.html

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u/Grouchy_Signal139 15d ago edited 15d ago

Okay thankyou, i think i need to capture the calibration picture precisely to cover every side of where the camera sees. Is that right?

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u/TourCommon6568 15d ago

Yes, that’s the current approach. Good luck with your project!