# Distortion Coefficients Units

I already checked other questions here in the forum about this but I did not find a good answer. I have to remove the lens distortion of a picture, my distortion coefficients are in k1mm-2, k2mm-4, and k3mm-6. But I do not get satisfactory results, I'm sure my data is correct, my question is whether I use my parameters the way they are (mm-2, mm-4, mm-6) or I have to do some transformation before?

Focal, cx and cy are correct are Ok.

Thanks

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what do you mean k1mm-2 ? isit in millimeter square inverse= 1/(mm * mm)?

( 2017-02-02 10:09:22 -0500 )edit

Yes, thats it...

( 2017-02-02 10:49:55 -0500 )edit

I think something is missing in your problem:"lens distortion of a picture" Do you mean you scan a picture?.

Where is opencv problem ?
how can you know k1 without calibration ?

( 2017-02-02 15:29:43 -0500 )edit

Sorry ... it's an aerial photo taken by a PhaseOne camera, IXA180. The camera was calibrated by another company that sent me the parameters. They also sent me a photo without the distortion and I'm trying to do the same with OpenCV but I do not have the same result. I'm sure the photo sent by them is correct, but they will not tell me how they did it.

( 2017-02-02 15:50:31 -0500 )edit

Are they perhaps k4, k5, and k6? If you look at this page, they are apparently the same units as k1, k2, and k3, but in a different part of the equation..

( 2017-02-02 18:18:40 -0500 )edit

If your coefficient are in mm (-2 or -4 , -6) there are two possibilities :

1. To calibrate camera companies print a grid on a paper and use this camera with this grid using optical table. You will have coefficients in mm
2. pixel size is 5.2 micrometer use this size to convert your coefficient
( 2017-02-03 01:56:54 -0500 )edit

The real problem is this: I have two cameras on a plane, side by side, one RGB with 80Mp and another InfraRed with 60Mp. The photos are taked at the same time. I need to generate a 4 band image, but the IR have don´t fit perfectly with the RGB photo. The two cameras are calibrated. What i´m doing, i remove the lens distortion from the photos, so i use ORB to detect some points, find a homography and use warpperspective to fit the IR on RGB. But i still finded small offsets. In the center of photos it´s 100% fitted. I can´t use SIFT or SURF because the photos are too big and i have problems with memory. I believe that the problem is in the undistortion process. I converted the k coefficients to pixel, dividing by pixelsize without sucess..

Sorry for my english.

( 2017-02-03 04:58:28 -0500 )edit

may be you should post a new question.