I am trying to calibrate a fisheye camera with 120° angle of view. The cv::fisheye::calibrate() function returns me the following error
OpenCV(4.1.0) Error: Internal error (CALIB_CHECK_COND - Ill-conditioned matrix for input array 15) in cv::internal::CalibrateExtrinsics, file c:\build\master_winpack-build-win64-vc15\opencv\modules\calib3d\src\fisheye.cpp, line 1421
I first tried using OpenCV 3.2 and get the same error. Changing the number of chessboard images does not affect the result. Here is the call of the function
cv::fisheye::calibrate(objectPoints, imagePoints, imgSize, cameraMatrix, distCoeffs, rvecs, tvecs, cv::fisheye::CALIB_CHECK_COND);
When using the same inputs with the cv::calibrateCamera() function, I get quite a good estimation of the camera parameters but I believe a fisheye model would be more adapted.