Darkly Labs Community

Camera Calibration

Are the Calibration files for the chessboard /circles available elsewhere other than in the documentation help section?

I’m having issues trying to download them. 

I’ve attached them here.  When you say you’re having trouble downloading them, how so?

Hi LightBurn, I thought I was going loopy, every time I tried to open the Calibration png. files all I got was a black screen. It appears that Windows 10 ‘Photos’ app is based on a black background and any photo with transparency is blacked out. 

I got around it by using a Windows 7 computer with its ‘Photo Viewer’ app and bingo there it was.

Thanks for your support - I don’t know if any one else has had this frustrating problem. 

Bob

Same thing happened to me, couls see them, thought something was wrong, then tried importing them to coreldraw and then could see them

Okay I have another question -
the chess board print is supposed to be 210mm x 297mm according to the documentation, which is basically a full size A4 sheet. But when you look at the photos of the chessboard being used inside the Emblaser it appears to be smaller.
Can somebody explain this to me ?

Which documentation are you referring to?

I’m measuring my chessboard, and it’s about 244.5mm x 171mm, printed on an 8.5 x 11 US letter page.

Here is the documentation link -

https://github.com/LightBurnSoftware/Documentation/blob/master/Using_a_Camera.md

It says -
'You’ll need to download and print the following two images:

Calibration-Circles.png Calibration-Chess.png

Do not resize them - The circles image will be approximately 148mm x 105mm (5.8" x 4.1"), and the chessboard will be approximately 210mm x 297mm (8.5" x 11").’

Apologies - The page it’s printed on in that photo is 8.5" x 11" - I’ll make a note to change the documentation. It is required to have a white border around the image, so it’s only half wrong.  :slight_smile:

Thank the Gods for that, I really thought I was missing something obvious. So now I’ve got your attention can you help me out with the camera calibration? I’m now using your recommended chess board size but it still is coming up with a strange result.My initial calibration was good - 10 captures with an average of 0.1, but when I went to ‘find chessboard’, this was the result -

 

sorry that would have been 0.8 calibration

That specific issue is something that’s sorted in the next release, which should be out early this weekend (it’s Friday here for us).

You beauty !
Thanks for working overtime for me LightBurn.

This is released as v0.7.00

Great !
Thanks LB

@LightBurn: quick question: I manage to calibrate the camera using the dot pattern, with an error of about 0.3. However, even after capturing >=6 images, and then closing the calibration tool screen with “OK”, it won’t actually save the calibration data. The camera view still is distorted, and re-opening the calibration tool doesn’t show any of the previous calibration data. Am I missing something obvious, or how does one save the calibration data?

 

  • Daniel

The camera preview window is always distorted, as it is a live feed from the camera itself. After doing the lens calibration and hitting “Finish”, the data is saved. Doing the chessboard capture then computes the mapping from the camera view to the workspace, and stores that information as well. Clicking “Update Background” from there will show the in-distorted view in the background of LightBurn itself.

The entire process is being rewritten and replaced with a wizard that walks you through it much better, and should be much simpler to follow, and we also hope to do a video walkthrough of it soon.

Dear LightBurn Team,

This is the first time I am trying to calibrate my camera but right after the first image, which scores about 0.31, I am not able to get any further. In most of the cases the pattern is not found. Or if it is, then the reprojection error is so large, that it is not proper for fine-tuning the calibration. I have attached an example image about this. Do you have any suggestion how shall I proceed or fix this, please?

May I ask which fisheye model do you use? If all else fails, then I will do the calibration and calculate the lens parameters myself. :slight_smile: But I hope there will be an easier way to do this…

Kind regards,
Zoltan

The system is just OpenCV, using the first five distortion parameters: https://docs.opencv.org/2.4/doc/tutorials/calib3d/camera_calibration/camera_calibration.html

From the image you’ve posted, it looks like you have the card “too vertical” - it should be parallel to the camera sensor, or as close to that as possible.  The second image is a bit painful to get because the bed of the machine makes the image slightly too close. You may need to move back a little to get the capture registered. You can also print the circles pattern slightly smaller.

Thanks a lot for the fast response, I am giving it another try!

Thanks again, it went better this time, I used a scale of 0.85 on the circle pattern. May I ask whether you have written a custom circle pattern detector or it is OpenCV based too?