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Camera calibration difficulties with 4 cameras

https://forums.naturalpoint.com/viewtopic.php?t=5291

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Camera calibration difficulties with 4 cameras

Posted: Mon Nov 12, 2007 9:02 am
by aweinstein
Hi:

I am now using 4 C120 cameras instead of 3. In the calibration process, during the Calculate stage, I get a Matrix Error most of the time. I tried with the different calibration option,with the same result:

This is the output I get:

Code: Select all

[STATUS] Begin Calibration:

09:01:14:937 Camera Calibration (c) NaturalPoint, Inc. 2007
09:01:14:937 Camera #0
09:01:14:937   PixelWidth : 355
09:01:14:937   PixelHeight: 290
09:01:14:937   FrameCount : 120
09:01:14:937 Camera #1
09:01:14:937   PixelWidth : 355
09:01:14:937   PixelHeight: 290
09:01:14:937   FrameCount : 120
09:01:14:937 Camera #2
09:01:14:937   PixelWidth : 355
09:01:14:937   PixelHeight: 290
09:01:14:937   FrameCount : 120
09:01:14:937 Camera #3
09:01:14:937   PixelWidth : 355
09:01:14:937   PixelHeight: 290
09:01:14:937   FrameCount : 120
09:01:14:953 Start Global Iteration [0] ==========================
09:01:14:953 Number of cameras fill: 1
09:01:14:953 Validation with tolerance threshold: 10.00 ...
09:01:14:968 [119] points survived validation and packing
09:01:14:968 119 points/frames have survived validations
09:01:14:968 Filling missing points ...
09:01:14:968 Fill bundle...
09:01:15:00 Change:354.988 DiffCols:36.194 DiffRows:18.131
09:01:15:00 Change:0.064 DiffCols:0.170 DiffRows:1.252
09:01:15:15 Change:0.000 DiffCols:0.013 DiffRows:0.092
09:01:15:453 Error balanced: 1.#INF00
09:01:15:453 info.err.no_fact = 1.#INF00
09:01:15:468 Change:1.#QO DiffCols:-100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000.000 DiffRows:-100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000.000
09:01:15:593 No convergence in 30 iterations
09:01:15:625 No convergence in 30 iterations
09:01:15:656 No convergence in 30 iterations
09:01:15:671 No convergence in 30 iterations
09:01:15:703 No convergence in 30 iterations
09:01:15:718 No convergence in 30 iterations
09:01:15:734 No convergence in 30 iterations
09:01:15:750 No convergence in 30 iterations
09:01:15:750 No convergence in 30 iterations
09:01:15:765 No convergence in 30 iterations
09:01:15:765 No convergence in 30 iterations
09:01:15:765 No convergence in 30 iterations
09:01:15:781 Beginning optimization pass
09:01:15:781 Matrix Error
09:01:15:781 Calibration complete
What can I do to improve the situation?

Re: Camera calibration difficulties with 4 cameras

Posted: Mon Nov 12, 2007 3:23 pm
by Birch
It sounds like it could either be a wanding issue and/or a camera setup issue.

Are the four cameras pointing toward the same capture volume area, and are the sync cables connected between the cameras?

Have you tried altering your wanding technique to go faster/slower or to cover a larger/smaller volume?

It might also help if you took a screenshot once you complete the wanding stage (but before advancing to the next stage).

Re: Camera calibration difficulties with 4 cameras

Posted: Fri Nov 16, 2007 2:28 pm
by beckdo
Alejandro,

Unlike the V100 cameras, calibrating higher camera counts on the C120s can be difficult. Here are a couple things to help you:

- Absolutely have to connect synchronization cables on the C120s for good calibration.
- Have all C120s pointed on a single central point. Do not attempt to expand your capture volume by pointing the C120s in various directions away from a central capture volume.

Good luck!

Re: Camera calibration difficulties with 4 cameras

Posted: Thu Nov 29, 2007 8:42 am
by aweinstein
Moving the cameras a little solved the problem.

Re: Camera calibration difficulties with 4 cameras

Posted: Thu Dec 20, 2007 4:08 pm
by beckdo
It can be challenging to calibrate the C120s. As you increase the number of C120s you find that it becomes more difficult to converge. Synchronization cables can help to a point, but there is no substitute for the higher resolution & quality lenses of the V100 cameras.

Re: Camera calibration difficulties with 4 cameras

Posted: Fri Dec 21, 2007 8:04 am
by aweinstein
It can be challenging to calibrate the C120s. As you increase the number of C120s you find that it becomes more difficult to converge. Synchronization cables can help to a point, but there is no substitute for the higher resolution & quality lenses of the V100 cameras.
I changed the camera position, and now I can run the calibration. However, as you say, it is difficult to get a good result (in terms of the standard and mean error).

Anyway, we are getting the V100 cameras, so this will not be an issue any more.

Alejandro.

Re: Camera calibration difficulties with 4 cameras

Posted: Mon Feb 18, 2008 7:33 pm
by beckdo
We posted an updated version of our software today. It included improvements to lens distortion calculation. Feel free to give it a try with your C120s.
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