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Calibration scale

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

Calibration scale

Postby william » Wed Apr 01, 2009 11:41 pm

Hi to one and all. What calibration scale is best for scanning chessmen, H=120mm,W=60mm and D=60mm ?.
Thank you William(Bill).
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Re: Calibration scale

Postby RAYA » Sat Nov 07, 2009 10:52 pm


For normal calibration method and if you stand it vertically ,you should divid 120 by 4,120/4=30,but add 20 persent to it,which mean 36 mm (distance between points on calibration panels).

Here and at up position your width has not matter.

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Postby hal » Sun Nov 08, 2009 11:04 am

Hello William,

you can do an "intuitive" valutation of the scale value by eye: place your object in front of the camera and near the panels (better if it's close to the background angle) and try to obtain the better view of the object. This means:
- the object must be well fitted with the camera view and you must see it in the center, using all the view space as you can;
- leave free the left and right portions of the panels (at least 1/4 of the view, where David can read the laser line ON the panels).

After, simply evalutate at fly the dimension of the markers's sheet and print it. All the markers must be fitted with the entire space of the camera view, just to have the better calibration of the camera.
At the end measure the scale value.

An other way is to print the markers's sheet just a little bigger than the object.
You can test the right size of calibration sheets with "The HotDog Test" :D :
- Print a sheet with the markers with a size that you consider ok for the object;
- Bend at 90° the sheets along the vertical black line;
- Put the object between the two bended borders of the sheet;
- If you are right, the object must be surrounded by the borders of the sheet and stay inside the set of markers;
- Pay attetnion to not cover the left and right areas of markers and keep the object close to the angle, in the center.

Now you can put some mustard or ketchup on the object, wrap and close the sheet ... and eat it! :lol:

Hope this can help,
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