Describe the doc issue

The page https://docs.opencv.org/4.x/dc/dbb/tutorial_py_calibration.html shows the lens distortion formula. It does not however explain what (x, y) and (x_distorted, and y_distorted) are. They are not raw pixels, as at least they need to be shifted to the origin. They are also likely normalized, but whether by focal length or by something else is also not clear.

It would be nice if this is explained.

Fix suggestion

No response