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Does the resolution of an image affect the distortion co-efficients

asked 2016-12-14 06:14:28 -0500

Prototype gravatar image

What parameters does the distortion co-efficients rely on. If I take an image with 2MP and another image with 12MP with the same camera , will the distortion co-efficients change?

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@Tetragramm and @berak , can you please help me with this

Prototype gravatar imagePrototype ( 2016-12-14 06:15:15 -0500 )edit

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answered 2016-12-14 07:28:25 -0500

Tetragramm gravatar image

According to : http://docs.opencv.org/master/d9/d0c/group__calib3d.html

The distortion coefficients do not depend on the scene viewed. Thus, they also belong to the intrinsic camera parameters. And they remain the same regardless of the captured image resolution. If, for example, a camera has been calibrated on images of 320 x 240 resolution, absolutely the same distortion coefficients can be used for 640 x 480 images from the same camera while fx, fy, cx, and cy need to be scaled appropriately.

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It depends of field of view too. May be 320x240 and 640x480 are same field of view but it is different for 1280×720

LBerger gravatar imageLBerger ( 2016-12-14 09:37:00 -0500 )edit

Ah, Right. I should point out that they don't depend on resolution if you're doing the resizing and altering the camera matrix appropriately. If you're changing settings on your camera, that can be different.

So if you take your input 640x480 image and use cv::resize to make it 320x240, as long as you update your camera matrix, that's fine. If you or your camera crops out the center 320x240 pixels, that's not fine, and needs a different calibration.

Tetragramm gravatar imageTetragramm ( 2016-12-14 17:32:28 -0500 )edit

@Tetragramm does the camera matrix vary for images caught in auto mode from different heights?

Prototype gravatar imagePrototype ( 2017-01-16 02:08:15 -0500 )edit

Depends on what auto mode is. If the focal length is constant, then all is well, no matter the height.

Tetragramm gravatar imageTetragramm ( 2017-01-16 18:10:37 -0500 )edit
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Asked: 2016-12-14 06:14:28 -0500

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Last updated: Jan 16 '17