Problem with calibration.cpp

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Hi everybody! I'm using version 2.4.3 of Opencv and more in detail the code calibration.cpp, for two camera calibration. My problem is that sometimes code works well and sometimes the output is completely wrong; it depends on the input images that I give to the program. My questions are:

1) Have you ever had this problem with the same code? 2) Are there specific indications for input images to the program? 3) I notice that extremely bad parameter during wrong computations is distortion: should I take photos with chessboard in the corners of the images to improve the computation of this parameter?

I can give you the images that give me wrong output.

I'm trying to upload the .zip folder of images in this web site but it seems it does not upload. How to do it? Thank you all in advance.