point pixel coordinates in undistorted images

[osima]

Dear All,

Based on the camera model estimated in Photoscan and coordinates of an object in a distorted image (col,row), I try to compute coordinates of the object in the undistorted image (col_und, row_und) provided by Photoscan.
I export the images without centering the principal point (but I also tried with this option enabled).
I follow the formulas provided in the user manual but cannot get the values right. There is only the radial distortion that is present in the images (all tangential distortion = 0, as well as the skew value).

I noticed that the undistorted image should be larger than the original, but the exported undistorted image is of the same size as the input image. I suspect this "crop" causes a shift in my computations but I am not able figure out what the sift is.

Could some shed some light on this subject? How to find coordinates of an object in the undistorted image exported in PS based on the camera model and coordinates of an object in a distorted image.

best regards,
Ola