Incorrect focal length by Camera Calibrator?

Hello,

I noticed that Camera Calibrator gives focal lengths approximately twice as big as OpenCV. This affects calculation of the field of view. I think that Camera Calibrator's values are incorrect as field of view provided by camera manufacturer and rough estimates of FoV obtained by myself match the OpenCV values. Is the Camera Calibrator's meaning of focal length different from the standard one?

Thank you,

Yuri Rzhanov

Answer 1

[Hornett]

The discrepancy you are observing might be due the fact that OpenCV spatial coordinate system specifies the upper-left pixel center at (0,0), whereas the MATLAB spatial coordinate system specifies the pixel center at (1,1). You can use the "cameraIntrinsicsToOpenCV" function to convert MATLAB "cameraIntrinsics" or "cameraParameters" object, specified by intrinsics, to OpenCV camera intrinsic parameters.

Take a look at the following documentation which can help you further.

• https://www.mathworks.com/help/vision/ref/cameraintrinsicstoopencv.html

Hope it helps!