title: Square size with asymmetric circles grid openCV
body: <p>I'm using OpenCV for a project about my thesis, I have to calibrate my camera for a recostruction3D. I have a question about square size, I know it is the size of a square when we use chessboard pattern, but I use circles grid or asymmetric circles grid. Can you explain me the meaning of this term in theese case?</p>
  
  <p>I thought that it hadn't influence and for the firsts set of a calibration didn't change that value fixing it to 50, but I try to change to curiosity and the results change. In particular way changes the closeness of <em>cx</em> and <em>cy</em> compared to ideal central point that I supposed in the center of image. If I put a big balue like 10000 for example, it's very very close, but I have a higher value of K2 (radial distorsion) and a similar Reprojection Error. </p>
  
  <p>Someone can help me to understand the reason???</p>