Correct images with Camera corrector

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Hi, I'm using the camera corrector application to correct a series of images that have barrel distortion using chessboards.
Following the steps below:
1.I attach the series of photos to be corrected with the different positions of the chessboard, without modifying the position of the camera.
2. I introduce the size of the different squares that make up the board. And frame that has a high distortion the image to process
3. I perform the processing of the different photos and press the calibration button
4. Detect the different points of the chessboard
5. And I hit the "show undistorted" button. To see the result of the correction.
Apparently the image is corrected. But using a photo correction program, I observed that this is not the case, that there are errors in its correction.
it is observed that the upper right corner is not fully corrected. I have carried out the same procedure with a smaller number of photos, with a different location of the chessboard, etc. I am somewhat confused. What could I do to completely correct the image?

Answers (1)

Image Analyst
Image Analyst on 13 Sep 2022
Looks pretty good to me. What sort of problems is it creating for you? Why do you need more accuracy? The distortion is probably computed as a regression through the detected corner points, and since it's a regression may not have subpixel accuracy for all points in the image. How much off is it and what problem does that cause in your analysis of the scene?
Your camera is also not pointed at the center of the scene and probably does not have the optic axis normal to the plane of the gray frame, thus causing skew/shear in the corrected gray frame. Is it super important that the gray frame be perfectly rectangular? If so, why? Try adjusting your camera so that the camera is at the center and perpendicular to the plane of the scene.
It might also improve if you made your checkerboard larger and put it near the center of the scene with its center on the optic axis.
It looks like you're using a very short focal length lens and are close to the scene, thus causing the fish eye (barrel) distortion. You could reduce the distortion in the first place by using a longer focal length lens, or course this would mean moving the camera farther away to get the same field of view, but maybe that's an option.
Pedrp Perez Serrano
Pedrp Perez Serrano on 16 Sep 2022
Thank you very much for your reply. In these photos I am not measuring anything yet, first install the panels to try to correct the image so that later I can measure the height of the fluid. Since if I install the panels at the same time that the fluid passes, it does not let me process it correctly.
I have decided to install larger panels to cover more surface of the image and also try to focus the camera on the center of it.

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