Recommendations for taking calibration photos

Contact person: Alexander Velizhev (avelizhev@graphics.cs.msu.ru)

Attention! Verify your calibration pattern size. If you have entered wrong object dimentions detection will run incorrectly. It runs only with calibration patterns using odd x even (or even x odd) number of squares (i.e 5x6, 7x8, 10x7, etc).

Recommendations

  • The white space (marked with red on the picture below) between the outer squares and the object boundary should be at least 1 square wide, like this:


    Figure 1. Calibration pattern

  • All the squares must be clearly visible (unoccluded).
  • Use a tripod
  • Take 25 images and more
  • Use a paper size ".3" and more
  • Square size is 3-5 cm
  • The chessboard on the images must be located in the all places of the camera matrix


    Figure 2. Point density

  • The chessboard must be plane
  • Take photos from these positions + from the top of the chessboard


    Figure 3. Camera positions

  • The tilt angle is constant (for example 45 deg)


    Figure 4. Tilt angle

  • Take photos with three camera positions


    Figure 5. Tilts of the camera

Another thing is that I actually tested only on my images, so maybe my modifications won't help other people to do their calibration. If so - send me your image sequences, I'll try to tune up my method to work with them also.