Recommendations for taking calibration photos


Written by Alexander Velizhev

http://research.graphicon.ru/calibration/recommendations-for-taking-calibration-photos.html

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 5×6, 7×8, 10×7, 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:

    Image

    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 

    Image

    Figure 2. Point density

  • The chessboard must be plane

  • Take photos from these positions + from the top of the chessboard

    Image

    Figure 3. Camera positions

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

    Image

    Figure 4. Tilt angle

  • Take photos with three camera positions

    Image

    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.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s