Optimum Calibration Size

The place for questions, problems, comments and tips regarding the camera calibration.

Optimum Calibration Size

Postby claytonread » Mon May 23, 2011 3:27 am

I am scanning handles at a length of about 32 inches or 82cm (see attached) I have my boards that are bigger this (each section is 85cm tall x 40cm wide) but I am wondering what would be the optimum size for the calibration points?

Any help would be greatly appreciated.

Kind Regards,
Clayton
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Re: Optimum Calibration Size

Postby CliveB » Mon May 23, 2011 7:35 am

Hi Clayton,

I usually make my calibration boards based on the height of the object to be scanned.
What you have submitted as your calibration size seems to be correct to me. I think that if you make some different sized calibration boards, you will find what best suites your needs.
You may want to try making some patterns that are half the height of your object to be scanned and placing those on your 85cm boards. I think they will work to. Personally I have found that if the calibrations are about 1/3rd the size of the background boards or smaller, I tend not to get immediate recognition by the DAVID program of the points and have to end up doing it manually or adjusting the contrast/brightness settings. I hope this has helped you.

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Re: Optimum Calibration Size

Postby WalterMo » Mon May 23, 2011 9:30 am

Hello Clayton,
And because your object is rather long in relation to its width you should rotate the cam for 90° and use the portrait format:
viewtopic.php?f=3&t=1432

At that time when the thread of above was created the old pattern sheets were used. But the newer V3 pattern are better and more universal because for DAVID's calibration it is only necessary that the 6 big dots are in the camera view. For the old pattern it was important that all the 24 dots and one double dot was visible.

Walter
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