Using OpenCV to calibrate Pi Camera always gives me the same fx and fy for focal length

asked 2018-05-22 01:58:08 -0500

Hi all,

I'm doing camera calibration using OpenCV's tutorial code from here.

As we know, the output camera matrix should in the following matrix:
[fx, 0, cx
0, fy, cy
0, 0, 1]

From that, the camera intrinsic matrix I got always has the same fx and fy. For example: data:
[ 6.5746697810243404e+002, 0., 1560, 0., 6.5746697810243404e+002, 1232, 0., 0., 1. ]

From the sample given by OpenCV, it also has the same fx and fy.

I don't understand why the calculated fx and fy will be the same, since the resolution for x and y is different, the sensor width and height is also different.

Is there anybody can explain this for me???

Thanks a lot.


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It is entirely possible that they are using the same camera, just resizing the image. Or, since the Pi camera is cheap, they used a commonly available lens and focal plane, which match up with the one used in the tutorial.

So long as it seems to represent your camera well, don't worry about it.

Tetragramm gravatar imageTetragramm ( 2018-05-24 18:52:29 -0500 )edit