Camera calibration

Camera calibration estimates the parameters relating points in a scene to measured image coordinates. In the ideal pinhole model,where $K$ contains focal lengths and the principal point, while the rotation matrix $R$ and translation $t$ locate the camera relative to the scene. Lens distortion requires additional parameters.^[ref]

A calibration experiment photographs a flat board with a known grid from several orientations. Detected grid corners provide image measurements; their known spacing supplies geometric constraints and a length scale. Parameters are fitted by minimizing reprojection error. Multiple orientations help separate camera geometry from board pose. For an ideal camera with focal length 1000 pixels, a point displaced $0.1\mathrm{m}$ sideways at depth $2\mathrm{m}$ projects 50 pixels from the principal point.^[ref]