How does cropping an image affect camera calibration intrinsics?

Question

I have the following camera matrices for resolution 1600x1300

M1 [3x3] =
    [ 1.3964689860209282e+03, 0.,                     8.3190541322575655e+02,
      0.,                     1.3964689860209282e+03, 5.9990987893769318e+02,
      0.,                     0.,                     1.                    ]

D1 [1x14] =
    [ 8.0832142609575899e-02, -8.0503813500794497e-02, -1.3722038479715831e-03, -6.9032844088890799e-04, 0., 0., 0., 0., 0., 0., 0., 0., 0., 0. ]

I need to change the resolution to 1280x720, but this resolution is a cropped resolution (not resized). I understand that I have to update cx & cy. Do distorition coeffients change after cropping operation?

Answer 1

No change, provided you adjust the (cx, cy) coordinates of the principal point to its new location in the cropped image. This is because the focal length does not change, and the nonlinear distortion model implemented by Opencv is referenced to the principal point.