MATLAB: Error after computing 3 coefficients of Radial Distortion for stereo Calibration

calibrationComputer Vision Toolboxstereo vision

When I performed stereo calibration by selecting the radio button 3 Coefficients for Radial Distortion, I was not able to view the rectified images. I got the following error:
My question is:
  1. Computing 3 coefficients for Radial Distortion along with Skew and Tangential Distortion increases Calibration accuracy, right?
  2. Why aren't the rectified images seen when I compute 3 Radial Distortion Coefficients? The images aren't rectified.
I have read this link, which says " Typically, two coefficients are sufficient for calibration. For severe distortion, such as in wide-angle lenses, you can select 3 coefficients to include k3."

Best Answer

From looking at your images, I would say that 2 coefficients should work. Using 3 coefficients does not always help. It adds an extra degree of freedom to the camera model, which may cause the optimization to become unstable.
The reason that rectification fails in this case, is that undistorting these images folds them upon themselves, and the function cannot determine the correct size of the output image. If you want to see what is happening, try exporting the stereoParameters object, and calling the rectifyStereoImages function with the 'OutputView' parameter set to 'full'.
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