title: OpenCV cannot find chessboard corners in fish-eye images
body: <p>I am using OpenCV3.0 and VS2013 to do fisheye wide-angle(185 deg) camera calibration. There are some pictures that can work well, e.g: </p>
  
  <p><img src="https://i.stack.imgur.com/ArbGq.jpg" alt="Chessboard to be detected-- fish-eye"></p>
  
  <p>and the correction result is satisfying as:</p>
  
  <p>![corrected image -- fish-eye][2]</p>
  
  <p>The result looks good, but I use a similar image to do calibration instead, it cannot find any chessboard corners!! The image is like this:</p>
  
  <p><img src="https://i.stack.imgur.com/ofTcV.jpg" alt="another chessboard image"></p>
  
  <p>The results are very confusing to me since I try many many similar images( same distance different angel, same angel different distance ) for about 60 images, and small part of them can be detected. I use 2592x1944 resolution BMP files, and I accurately put the chessboard center in the center of camera, but the result is no good than the casually captured images, some even cannot find corners. 
  I use this code to detect:</p>
  
  <pre><code>bool patternfound = findChessboardCorners(imageGray, board_size, corners,CALIB_CB_ADAPTIVE_THRESH + CALIB_CB_NORMALIZE_IMAGE+ 
          CALIB_CB_FAST_CHECK );
  </code></pre>