Vision provides a maximum rectification error and a rectification quality metric to indicate the quality of rectified images.

These parameters are computed using epipolar lines, which are obtained with the fundamental matrix produced during stereo calibration. For example, an epipolar line for an image obtained with the right camera describes the 3D vector of a point relative to the center of projection for the left camera. A valid match in the right camera image must lie on the epipolar line. The following figure illustrates an epipolar line in the right image plane:

The maximum rectification error indicates the greatest distance between a point and its corresponding epipolar line. If this error is greater than 1 consider repeating the calibration process.

The rectification quality metric is a value between 0 and 1, with 1 indicating perfectly aligned rectified images. If the rectification quality metric is less than 0.7, consider repeating the calibration process.