7 votes

camera calibration: why chessboards?

This is mostly a matter of history. Checkerboard patterns have proven in the past to: yield calibration accurate results be easy and robust to implement. This was confirmed (for example) by a ...
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  • 3,889
6 votes
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Is it possible to hack camera calibration without having access to the camera?

If I understand correctly, you don't need the intrinsics or extrinsics to achieve that, if a top-down view is all you want. You could basically define 4 points on your parallel lines and then warp the ...
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  • 5,207
4 votes

camera calibration: why chessboards?

You can use any target you'd like as long as you can find the features in a robust way, and you know their location in the real world. For example I used once ISO12233 chart image to calibrate radial ...
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4 votes

Camera Calibration - why do you have to move the calibration board?

This is due to the optimization problem being rather high-dimensional (around 11 parameters). With only a single observation of the calibration board, there would be multiple possible combinations of ...
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  • 146
3 votes
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Can you average out focal length from different camera calibration sessions?

No, it is not a good idea. Typically, you want to limit the volume of space relative to the camera in which you want to do your measurements, and you want to use a single calibration target ...
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  • 4,911
2 votes

Image processing and Camera Calibration

Yes, the center pixel and focal length in pixels will change, as described in the link above. However, if you learn distortion parameters (radial and tangential) then they shouldn't change as ...
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2 votes
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How does chessboard configuration affect camera calibration?

Generally speaking, when you are estimating a model from data, the more (independent) data points, the better the estimation. In this particular case, the goal is to get as many 3d -> 2d point ...
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2 votes

Camera Calibration using Single Input Image

Take a look at this paper here: "Straight lines have to be straight" by Faugeras et al. http://link.springer.com/article/10.1007/PL00013269#page-1 It is straight forward to implement, but essentially ...
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  • 61
2 votes

Camera calibration using multiple images

You are correct: to calibrate a camera you need a correspondence between 3D world points and 2D image points. The problem is that the 3D points cannot be co-planar, so people were building 3D ...
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  • 4,911
2 votes

How to estimate radial distortion from lens characteristics?

There is a lot of variability because distortion can be compensated for optically and lens designs differ. Some lenses are marketed as rectilinear, most not. You would be making the distortion worse ...
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2 votes
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Pinhole camera model from houdini parameters

This is a long topic to fully explain. I will try to write shortly, so please excuse the brevity. Standard computer vision projection (ignoring distortion like Houdini) follows: $$ \mathbf{x} = \...
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  • 5,207
2 votes
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Camera calibration vs. registration

There is no matrix that maps a pixel in camera 1 to the corresponding pixel in camera 2. This is because the location of the corresponding pixel depends on the 3-D location of the corresponding point ...
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  • 4,911
2 votes
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What are the parameters of a calibrated spherical camera?

...if we have a pinhole camera model several parameters describe the specific camera (such as aspect-ratio, focal length, principal point, distortion parameters etc). "Distortion parameters" does not ...
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  • 10.1k
2 votes

Fixing distortion in photographic reproductions

I answered a related question in SO some time ago. Briefly, you can work your setup through a standard camera calibration procedure, and you have the option of "freezing" the focal length to ...
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1 vote

Camera calibration and extrinsic parameters for perspective transformation

For your application, here are the steps I would follow: Calibrate the camera and obtain the intrinsics - You have obviously done that and corrected for the distortion already. ...
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  • 5,207
1 vote

computer vision - How to correctly calibrate my camera with a wide angle lens using openCV?

If you haven't followed this tutorial on camera calibration with OpenCV, do it. It's well explained and the code is pretty much ready to go. And if your goal is to calibrate your camera using the ...
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1 vote

Why are two cameras mounted in paralle in stereo application?

When you say cameras are parallel it only means that the center pixels are parallel. Every pixel has a different angle, and that refers to the overlapping regions you were talking about. Actually ...
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  • 471
1 vote

the position of image plane in optical imaging

I agree with user lxg that it is a notational difference, as for the pinhole camera we always have: $$S_2 = f$$ That is not necessarily true for a camera with a lens. A pinhole camera is not the ...
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1 vote

How can we combine 2D image with 3D image for the same sense?

Formally speaking, you would like to extrinsically calibrate the laser scanner to the 2D image. I have taken the liberty to edit your question to reflect that. Here is how my initial approach would ...
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  • 5,207
1 vote
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Which pattern (circle pattern or checkerboard pattern) should be used for automotive camera calibration (fisheye/wide webcam)?

The answer here suggests that checkerboard patterns may yield more accurate (subpixel) calibration results and be more robust. You may have edited your question because the title asks which pattern ...
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1 vote
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How are the scaling parameters included (extracted from) an essential matrix?

The Essential matrix is defined only up to scale, so you cannot extract scale from it. In other words, if you multiply $t$ and all the 3D world points in your scene by a constant factor, the essential ...
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  • 4,911
1 vote

Obtain motion between image features by means of the homography matrix

First, calibrate your intrinsics: The focal lengths and the principal point. Homography is not really a rigid transformation and rather a mapping of a plane onto another one. What you really need is a ...
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  • 5,207
1 vote

Camera calibration using multiple images

So here are the answers to the questions: It's a good question. First, your calibration grid should somehow be "coded". For example, the OpenCV checkerboard pattern is a rectangle and the points are ...
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  • 5,207
1 vote
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How can I get a equation of slope?

Your $b$ is wrong. Take a look here. The form $y=mx+b$ is called Slope-Intercept form where $b$ is the intersection with the y-axis (which is 1 in your case). You should use the two-point form: $$ y - ...
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  • 1,440
1 vote

Pinhole calibration

It is possible to invert the mapping, but projecting a 2D image point into 3D world won't give you a single point but a ray, which is the locus of all 3D world points that map to the same point in the ...
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  • 126
1 vote

Changing camera and image properties to calibrate a camera

You should not experience any major drawbacks. Generally such techniques utilize adaptive thresholds and rely on gradient orientations (especially normalized ones), which are intrinsically invariant ...
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  • 5,207
1 vote

How to calibrate three orthogonal cameras?

For pairwise stereo calibration try using the Stereo Camera Calibrator app in the Computer Vision System Toolbox. It is much easier to use than Caltech Camera Calibration toolbox. For starters it ...
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  • 4,911
1 vote
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How to calibrate three orthogonal cameras?

Use an asymmetric calibration plate. Such as the new circle grid in OpenCV. Check here. You do not need to find the correspondences in the gui, but rather run the calibration directly. Also, do not ...
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