The camera doesn't find the lens calibration pattern (no pattern found)

The most common problems people have with the lens calibration are as follows:

  • Honeycomb bed is visible, confusing the circle-finding code. Cover the honeycomb with a bed sheet, cardboard, paper, wood, etc.

  • Camera isn’t in focus. Focus the camera as well as you can to get a clear image.

  • Calibration pattern is too small in the view - you want the pattern to fill roughly one of these squares for each capture:
    image

  • Calibration card printed incorrectly - if it doesn’t have exactly this dot pattern, it printed incorrectly:
    image

  • Poor or uneven lighting - If the card is unevenly lit, or part of it is in shadow, the circle finder can have a hard time detecting the pattern.

  • Make sure the card is directly facing the camera if you have a fisheye lens, or parallel with the camera lens if you are using a distortion-free lens.

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