OpenCV Q&A Forum - RSS feedhttp://answers.opencv.org/questions/OpenCV answersenCopyright <a href="http://www.opencv.org">OpenCV foundation</a>, 2012-2018.Sun, 16 Feb 2014 22:59:24 -0600CameraCalibration -> Documentation -> Focal Lengthshttp://answers.opencv.org/question/28465/cameracalibration-documentation-focal-lengths/Hi, everyone.
I have one question about FocalLenght in documentation in CameraCalibration.
Now we have formula like this:
![image description](http://docs.opencv.org/_images/math/dbe76ed3ef28b501c3933a74618c2c94889d38fa.png)
<br>
Why do we multiply by Fx and Fy in the last two rows, but not in the second and third rows?
In my opinion we should use this rows:
<br>
......<br>
x' = Fx * x / z<br>
y' = Fy * y / z<br>
......<br>
u = x'' + Cx<br>
v = y'' + Cy<br>
<br>
Am I right? Or I do not understand something?<br>
Can somebody help me to find error?
**EDIT**:
![image description](/upfiles/13928892586954167.png)
<br>
<br>
For simplicity lets consider only Z and X. Lets Y = 0 everywhere. <br>
<br>
D(x) — it is distortion polynom<br>
x — original point coordinates (X and Zx axises)<br>
x' — it is undistorted (ideal) coordinates (X and Zx axises) <br>
x'' — it is distored (real) coordinates (X and Zx axises)<br>
v — it is distored (real) coordinates (V and Zv axises)<br>
<br>
In my opinion to calculate image coordinates (V and Zv axises) using camera coordinates (X and Zx axises) we should use these equations:<br>
x' = f * x / z<br>
x'' = D(x')<br>
v = x'' + c<br>
<br>
There is my mistake?<br>
Why in OpenCV documentation we multiply by focus at the end, but not at the begin?Maxim MikhisorSun, 16 Feb 2014 22:59:24 -0600http://answers.opencv.org/question/28465/