Camera Calibration Image Print at its Original Size = Larger than Advised

Watching the video linked from the documentation on camera setup and calibration, it is advised to print the image out at its original size. The challenge is, the image is 1748 x 1240 in its linked PNG format (big / not roughly a ¼ of a standard sheet of letter paper). I can scale the print and get close to what is suggested in the instruction, but how critical is this scale?

Maybe the linked calibration file would be better as a PDF to provide consistency of scale.

Never mind… but for anyone else who becomes challenged in this situation, let me spare you the embarrassment. MS Paint then click File(Icon on the top left) -> Print -> Page Setup -> Scaling -> Adjust to 100% normal size.

The size of the print is really irrelevant - it’s the size in the camera view that’s important. Try to match the placement and size of the sample image, at least roughly.

So If I have a larger bed size, I could print the dot sheet out to a full 8.5x11 to help the camera pick up the image better? Also, I have a 170 deg camera, do I need to angle the card toward the camera some, if so, how critical is the angle to the camera to successful calibration?
This is the one I have, It is only 2MP, is that going to be a problem too?

You have two potential issues:

  • Higher angle cameras produce more distortion on the sides of the image, and compress the image together there, so the sides will be less accurate than the middle

  • Higher resolution is generally recommended for larger machines - You’re looking for more image pixels distributed over the area of the bed

Those will work against you a bit, but if you want it for rough placement (within a mm or two) it should be fine. You will need to angle the card toward the camera for that lens, and that’s ok - it’ll still be able to measure the image distortion just fine. Make sure you attach the card to something flat, like MDF or foam-core poster board. If the card is warped or curled, the software will treat that as lens distortion and try to correct it.

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There are two posts that discuss camera calibration that you should read as well:

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