Trouble with Camera Calibrator

I'm using the cameraCalibrator to generate image parameters using the supplied chessboard. This is all fine, however, when outputted my image intrinsics have a resolution of 720 x 1280, despite the inputted raw image being 3024 x 4032.

This means that I cannot use undistortImage function due to getting the error

Image size is not consistent with camera intrinsics. It is likely that the image is not generated by the specified camera.

despite the fact that the images were taken on the same camera and the files display the same resolution in Windows.

I can provide my code but I'm mainly following info from

https://uk.mathworks.com/help/vision/ug/structure-from-motion-from-multiple-views.html

https://uk.mathworks.com/help/vision/ref/cameracalibrator-app.html

I can't even see a way to adjust any of the outputs in the cameraCalibrator app, what am I doing wrong?