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Does anyone know the focal length(mm) of RGB camera?

asked 2015-05-20 21:10:11 -0600

gmir gravatar image

updated 2015-05-25 06:30:28 -0600

Image size is 640*480.

I don't know whether I'm right or not. As the focal length in pixels is 525(default) and the pixel size is 2.8 um, then the focal length is 525*2.8 um = 0.147 cm, which is needed to use my robot model.

I've used this parameter to implement conversion from image coordinate to camera coordinate. But it turns out a big error.

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I could be wrong but to me it seems you are trying to calculate 3D (Camera-) coordinates of a point using it's 2D (Image-) coordinates. That's not possible without the use of a stereo camera or a structure from motion approach.

Malefitz gravatar image Malefitz  ( 2015-05-29 08:14:54 -0600 )edit

It is possible if the real object dimensions are known. cv2.solvePNP provides a simple method for that, see:

Oscar Lima gravatar image Oscar Lima  ( 2020-07-09 06:58:20 -0600 )edit

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answered 2020-07-09 06:56:26 -0600

This question has been answered here:

Basically use this formula:

f = (width/2) / tan( deg2rad(hfov)/2)

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Asked: 2015-05-20 21:10:11 -0600

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Last updated: Jul 09 '20