stereo camera calibration error

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DavideC on 19 Dec 2020
Answered: Kevin Mallery on 7 Mar 2022
Hi all,
I am implementing a simple program to calibrate two cameras and compute a disparity map. I was given a set of 425 pictures of a chessboard, taken using the two cameras. Using the "Camera Calibration" tool I calibrated each camera individually, and I selected the images with reprojection errors lower than 0.7 (I kept about 70 pictures for each camera). Then, I calibrated the stereo pair using the same set of images.
The issue is that when I load the fixed intrinsics in the "Stereo Camera Calibration" tool, I get the following error message:
The value of 'principalPoint' is invalid. Expected principalPoint to be positive.
I am new to computer vision and I am pretty sure that I am doing something wrong.
I tried to compute the disparity maps without single-camera calibration. I got very poor results, and I think that it is due to bad camera calibration.
Thank you in advance for your help.
Have a nice day!

Answers (2)

Vinai Datta Thatiparthi
Vinai Datta Thatiparthi on 22 Dec 2020
I noticed a similar discussion on the forum that could be relevant to solving the error that you're reporting:
Hope this helps!
  1 Comment
DavideC on 24 Dec 2020
Unfortunately, my issue concerns the "Principal Point" and not image size.
Thank you for your answer.
Have a nice day!

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Kevin Mallery
Kevin Mallery on 7 Mar 2022
I'm getting the same error. So far, all I've been able to figure out as a "solution" is to just disable the positivity check in the checkPrincipalPoint function in cameraIntrinsics.m. As far as I can tell, I don't see any reason why the principal point should be constrained to be positive.
Could someone at Mathworks comment on this? I would prefer a solution that is less hacky.

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