I use this reference https://automaticaddison.com/how-to-perform-pose-estimation-using-an-aruco-marker/ to estimate pose of a marker.
When I obtain cam matrix and distortion matrix I used the full camera resolution.
However, when I change the resolution (image size) before pose estimation, I am getting different results. I am not sure why and which resolution would be correct to use.
Should we always use the same resolution as what was used for camera calibration?
I expected the pose to be somewhat independent from image size other than minor changes. Any thoughts?
Yes, always use the same resolution.
One could recalculate the camera matrix and distortion coefficients to fit a different resolution but that's a hassle, and requires some knowledge of how the camera made these pictures (binning, cropping). Unless you understand the math behind it, just stick with same resolution.