Incorrect result from camera calibrator app
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cr
am 18 Mär. 2024
Kommentiert: Alexander Groeger
am 2 Mai 2024
I used the camera calibrator app to calibrate lens distortion and I specified correct checkerboard size of 8mm. The calibration goes fine and i'm able to undistort images and points. However, the plot from showextrinsics() shows camera at 8mm distance from object but in reality it is 140mm. Why is this wrong?
My setup has a camera looking downwards and pattern is placed at the same working distance in all 30+ images where the lens is focused.
Calibration settings: All default settings - Standard lens, 2 coeffs, no tangential distortion, no skew, etc.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1645106/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1645111/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1645116/image.png)
4 Kommentare
Giridharan Kumaravelu
am 19 Mär. 2024
Would you mind providing us with the calibration images to help troubleshoot this behavior?
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Giridharan Kumaravelu
am 22 Mär. 2024
Bearbeitet: Giridharan Kumaravelu
am 22 Mär. 2024
Thanks for providing the calibration images. This is a limitation of the technique (Zhang's algorithm) that camera calibrator app uses, that it cannot calibrate a camera with calibration images that are coplanar. To accurately calibrate a camera with the app, you need some variance in the calibration images in the z-direction. Even a little wiggle in the z direction could avoid this degenerate configuration.
6 Kommentare
Alexander Groeger
am 2 Mai 2024
I'm not an expert in this field but I think the telecentric (aka orthographic) cameras requiere a different camera model for calibration. Since in the case of orthographic projection the Z-dependancy of magnification is eliminated (constant magnification instead).
For my application I'm currently working with a model based on Chen et al's work:
But I still think it would make MW's camera calibrator app more complete if an orthographic model would be integrated as well.
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