Questions tagged [camera-calibration]

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3D-to-3D pose estimation

Given a set of 3D points with their coordinates in 2 different coordinate systems, what is the correct algorithm to use in order to estimate the relative rotation and translation of the coordinate ...
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How is focal length estimated?

There are a number of approaches to calibrate cameras. In this process you estimate the intrinsic parameters using a checkerboard of known size. I'm confused on how the focal lengths are found. The ...
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Camera Calibration: Intuition for the extrensic parameters in relation to the camera center and intrinsic parameters

In our lecture we have learnt that the extrinsic parameters would transfer a point $X_\text{World}$ described in world coordinates to a point $X_\text{cam}$ in camera-coordinates In in-homogeneous ...
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What is the calibration method of this stereo camera?

I have a stereo camera setup from "QuantifiCare" Company that specifies for 3D reconstructing image of a human face just by 3 images. Everything is working well but I like to know the method ...
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Image Z Coordinate Clarification

I'm trying to understand 3D image reconstruction, and want to clarify how we can find a z image coordinate. Is the z coordinate for image coordinates (x,y,z) the focal length since that's the distance ...
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Is it possible to extrapolate a camera intrinsics matrix when calibrated at a different focal length?

I have to calibrate a camera with a variable focal length and that I'm going to use for long focal distances (>3m). I have a big chessboard target, but if I position it at more than 3m from the ...
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Reprojecting an image to another viewpoint using planar homography

I have an image rendered by a simulated camera in Unity. Using this image and the known (virtual) camera pose it corresponds to, I would like to render a new image from another viewpoint. Having read ...
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How to improve accuracy of camera extrinsics calibration

I have a multi-camera system where the field of views are mostly non-overlapping. I have been researching on methods to calibrate the camera extrinsics and the first thing I'm going to try is to take ...
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What is the purpose of the camera coordinate frame in the forward imaging model?

I am new to computer vision and was watching this lecture on camera calibration. I will use a diagram from the lecture for reference. From what I understand, a ray of light that is emitted from a ...
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Calibration using Camera Calibration Toolbox for Matlab vs OpenCV

I am currently working to calibrate a camera and I tried using both the Caltech Camera Calibration Toolbox for Matlab and OpenCV. I used the same images for both methods. Even if the error seems to ...
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Best targets to calibrate camera with long focusing distance

I am currently using a number of cameras with long focusing distance, i.e. >3m, and I want to calibrate them to find the intrinsic matrix. My problem is that if I want to cover all or most of the ...
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How to apply rotation to extrinsic and intrinsic camera parameters post-calibration?

I currently have a set of intrinsic / extrinsic camera parameters, and am using them to project 3D world coordinates to the 2D image, using projection matrix $P = K[R | t]$. My problem is that this ...
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Rotation and translation from Fundamental Matrix

I understand how to extract rotation and translation from the essential matrix. However, I did not find anything about obtaining the rotation, translation, (and also the calibration matrix) from the ...
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Camera calibration using checkerboard instead of 3D calibration object

What is the purpose and advantage of using a checkerboard than a 3D calibration object for camera calibration ? With a 3D calibration object (e.g. a transparent cuboid like a table), I can take one ...
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Equation of line in the Homogeneous coordinate system

Given two points P and Q we can convert them to the homogeneous coordinate system, compute their cross product and thus get the ...
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Find camera tilt

If I have a camera that captures tilted images what is the way to find the tilt of the camera? Is there a pattern that I can photograph or something similar. I want to reduce the tilt as precisely as ...
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How does image rotation affect the intrinsic camera parameters?

I am considering the problem of how to (manually) change camera model parameter to make it "valid" on a rotated image. This question tackles resizing, but does not consider lens distortion. ...
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Fisheye Lens Calibration for precision

OpenCV library offers a fisheye calibration method. I have looked at the code and looked at some papers and still don't understand how it works completely. The reason why I am interested is following: ...
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How to calculate the plane at infinity? either in Matlab or Python

I tried to implement this function to compute the plane at infinity $n_\Pi$ from the equation: where $w^{-1}$ is the image of the absolute conic IAC, $M_j$ is the Projection Matrix of image $j$, but ...
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Understanding legacy code: Algorithm to remove radial lens distortion

The method below to remove lens distortion from a camera was written more than ten years ago and I am trying to understand how the approximation works. ...
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How can I infer the cost function from Kruppa's simplified equations

The following equations are Kruppa's simplified equations used in camera autocalibration. My objective here is to infer the cost function(Error Function) from this equations, So I can minimize the ...
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Calibrating cameras with different resolutions

I have two cameras with very different resolutions. One camera is the RGB camera of the microsoft kinect sensor with a resolution of 1920x1080 and the other one is ...
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Camera Pose Estimation from Vanishing Points

I want to estimate the pose of camera (Location and Orientation). Can I use Vanishing Points to get the location and orientation of the camera? There is object in the image which I also know his size,...
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Virtual camera from panorama

I'm trying to virtualize a camera from a panorama. That is, suppose I have a really big picture, for example: a soccer field. Then I want to simulate a camera that focuses on certain regions of the ...
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1 answer
231 views

What are the parameters of a calibrated spherical camera?

I'm aware if we have a pinhole camera model several parameters describe the specific camera (such as aspect-ratio, focal length, principal point, distortion parameters etc). There're standard ...
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Bundle adjustment optimization parameters

While reading the Wikipedia article on Bundle adjustment, I came across the following objective function used to represent the bundle adjustment problem. I have two questions regarding this objective ...
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1 answer
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Measure object planar displacement on slight moving or vibrating plane

I'm working in an application where I'm tracking an object 2d displacement on a given plane and the camera is already calibrated (intrinsic) and the lens distortion has been corrected. In order to ...
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Camera Calibration - why do you have to move the calibration board?

I understand the mathematical derivation of Zhang's Method for camera calibration but what I don't understand is why we need to move and rotate the calibration board for several frames in order to get ...
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1 answer
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Camera and laser scanner calibration final approach questions

A while ago I posted this question about camera and laser scanner calibration. I've been away from this project for a while and now I need to come back and get a final approach to calibrate properly ...
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Camera calibration and extrinsic parameters for perspective transformation

I'm working in a photogrammetry camera and laser application where I need to measure a displacement in a specific plane, this is a quick diagram of the setup: In order to get proper measurements I'm ...
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computer vision - How to correctly calibrate my camera with a wide angle lens using openCV?

I am trying to calibrate a camera with a fisheye lens. I therefor used the fisheye lens module, but keep getting strange results no matter what distortion parameters I fix. This is the input image I ...
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Pinhole camera model from houdini parameters

From a simulation with Houdini software I retrieved these parameters: Camera position: -0.675839, 33.5945, 0.0318854 Camera Rotation: 0.0318854, 92.4693, 0.1 Focal Length: 52.5172 mm Image size: 1920 ...
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3 votes
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Correct Fish Eye camera Radial Distortion and blurry effect at the image edges

There are a lot of questions regarding this topic ,but I am trying to get a more clear picture from these questions. I am trying to calibrate a fish eye camera and I am using OpenCV omnidir class ...
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Estimating exterior camera parameters by matching lines using least square estimations (Lowe, 1991)

I'm new to computer vision and graphics. I want to estimate exterior camera parameters using non-linear least square estimation as suggested by "Lowe, David G. "Fitting parameterized three-dimensional ...
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Why are two cameras mounted in paralle in stereo application?

For stereo cameras on the market, two cameras are always mounted side by side and with a displacement that is perpendicular to the cameras’ optical axes. I take this setup for granted. One idea came ...
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the position of image plane in optical imaging

In the book Learning OpenCV, there is one figure that show the image plane always is focal image. The description of the figure from the book is as follow. We begin by looking at the simplest model ...
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How can we combine 2D image with 3D image for the same sense?

We have 3D point cloud data captured by a laser scanner and need to register it with 2D images to get further information. In our case, the 2D image and 3D points are not overlapping and therefore we ...
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Extrinsic Camera Parameters without introducing control points?

I am new to the field of Camera Calibration. We have successfully calibrated our camera through classic method (using checkerboard etc). I recently realized there is a field of research for Automatic ...
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2 votes
1 answer
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How should calibration points be distributed?

I do camera calibration for a single camera with a chessboard pattern in opencv for the first time. The focus is fixed. I'm not sure how to do it, there seems to be many questions: How many images ...
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Which pattern (circle pattern or checkerboard pattern) should be used for automotive camera calibration (fisheye/wide webcam)?

Calibrating a Fish-eye camera / webcam with large angle mounted on car by using opencv 3 One important issue is to define the calibration pattern and its position !!!! The affects error that paly an ...
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camera calibration change orientation of axis

I want to solve for the extrinsics by using direct linear transformation on corresponding 3D LIDAR points and 2D camera points. I already have the intrinsics. Problem is, points behind the camera ...
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4 votes
1 answer
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How are the scaling parameters included (extracted from) an essential matrix?

An essential matrix relates corresponding points between two images assuming that a camera satisfies the pinhole camera model, and can be expressed as: $$E=K'^TFK$$ where K is the calibration and F ...
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4 votes
1 answer
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Obtain motion between image features by means of the homography matrix

I have been reading several really good answers about how to obtain camera pose (rotation, translation, etc), such as this one and this one, but I am not sure how this applies to my problem. My ...
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In which way do image transformations change camera extrinsics?

Given a pinhole camera model, we have an image and according camera intrinsics K and extrinsic parameters R. When we scale the ...
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Camera calibration vs. registration

Suppose I have two cameras, c1 and c2 that are securely installed and do not move. What I want is a matrix T, that takes a pixel of an image from camera c1 and calculates the according pixel in an ...
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4 votes
2 answers
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camera calibration: why chessboards?

Chessboards are very frequently used for camera calibration, this website also talks a bit about why: wiki. One of the reasons is, that chessboards define many natural interest points. Now my (very ...
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4 votes
2 answers
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How to estimate radial distortion from lens characteristics?

Is there a way to estimate the radial distortion coefficients without calibration, given the lens characteristics, such as its diameter and its focal length? Typically for camera calibration a ...
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How to find the actual size of an existing object from the pixels of an image?

I am quite new to vision and OpenCV, so forgive me if this is a stupid question but I have got really confused. My aim is to detect an object in an image and estimate its actual size. Assume for now ...
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2 votes
2 answers
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Camera calibration using multiple images

I am trying to get the hang of camera calibration. For this purpose, I have mainly watched this lecture on youtube: Lecture 12: Camera Model by UCF CRCV. I believe that I understood the main ideas: ...
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How can I get a equation of slope? [closed]

Here are two $x$,$y$ coordinates: $(2,2)$ ,$(4,3)$. And I want to know if I choose $x$ between above coordinate. How can I know the $y$? As I know a slope of line equation is like this. $$y= mx+b$$ ...
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