Although image is displayed, the calibration pattern isn't found

I’d like to use an old mobile phone (Samsung Galaxy A3) as camera for LightBurn.
For that I’m running Iriun v2.7.6 which works fine.

However, when I try to run the calibration wizard it never finds the pattern despite it being perfectly visible in the preview image.

I tried different size printouts for the pattern, multiple backgrounds and all kinds of camera resolutions.

Can it be that a camera can be too good to be used?

Not likely.

A few tips:

  1. resize the pattern or increase focal distance. The pattern should fill roughly one grid of a 3x3 grid.
  2. not sure if it’s just me but the calibration pattern you’re using looks distorted. The circles appear elliptical. You need the pattern to be without distortion
  3. there is curling on the paper that you’re using. You need this to be dead flat to reduce calibration distortion. Once you can get the basic pattern to be recognized I suggest you paste the paper to a known flat surface.
  4. experiment with different lighting conditions. Slight differences can make a huge difference in score.
  5. if it’s easier you can calibrate the lens away from the laser. Try anything to confirm that the pattern is getting found. Once it does you can experiment to improve the score.
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Thanks for the reply :+1:

  1. I have tried a smaller version of the pattern, but maybe not small enough. I’ll test an even smaller one.
  2. On the actual printout they are proper circles, but depending on the chosen camera resolution they get distortet. However, I tried all possible resolutions (some distorted, some not)
  3. I’ll try that too.
  4. I did, but since I’ll be trying some more, that will get added to the list too :blush: :see_no_evil:
  5. roger that!

BTW, is it important to have the pattern perfectly straight/orthogonal to the X/Y axis each step of the way?

I believe this depends on the lens type. The reference illustration in the Calibration wizard will guide you as to whether or not the pattern should be angled toward the lens or not. I think it’s typically fisheye lenses that require the pattern be angled toward the lens.

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It finally worked :+1:

My main problem was that even my pattern shrunk by 40% was still to big. I had to reduce it by 60%.

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