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opencvroboticscamera-calibrationcalibration
Houssam Badri
Houssam Badri

Reputation: 2509

What is the purpose of calibrating in OpenCV?

I am starting a new robotics project (with cameras), so i need to calibrate its two cameras.

My question is: why do i need to calibrate cameras? Does it have any relation with defining object dimensions and distance to camera?

Any information could be helpful.

Thanks in advance

Upvotes: 2

Views: 397

Answers (1)

bergercookie
bergercookie

Reputation: 2760

Camera calibration (and more generally) instrument calibration is an essential prior step for pretty much any application you want the device for.

For example suppose you have a single camera. In this case you would have to calibrate it (i.e. compute the values for) for its intrinsics parameters (focal length, principal point, skew coefficient). You would do that using a calibration board (e.g., Checkerboard, AprilTag).

Now, you may say that these parameters are known and reported by the manufacturers of that camera and we can look them up either at the manual or at its corresponding documentation. However that's not always the case:

  • Manufacturers might provide you with that calibration information. Even if they do though, those numbers would probably be rough so that they address the whole family of products. That is, they'll probably not going to calibrate every single camera. You could use these calibration parameters but if you want higher accuracy you are better off using them as a rough estimate and do the calibration yourself.

  • The device may be affected by the environment and the overall conditions it is operating in (temperature, humidity etc.). For example, say you have a stereo camera. In that case you would calibrate for the length between the two independent RGB cameras. But that length may change depending on the temperature (heating will make the rigid link between the cameras expand).

  • The specifications of the device may change depending on the its age and usage so it makes sense to recompute its calibration parameters every N number of years.

All in all, by all means calibrate your cameras yourself. You'll be surprised at how significant this is.

Take a look at the following links for more information:

Upvotes: 2

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