Why reprojection error is minimized instead of triangulation error for bundle adjustment?

Question

For bundle adjustment optmization why is reprojection error minimized instead of traingulation error or ray-to-3d point error? Disadvantage with reprojection error is: for perspective camera, its highly dependent on depth of the camera from the point in 3d right.

Answer 1

If you would minimize triangulation error, you could easily end up in a local minimum, especially for intrinsic params - because the error would be the same for all cameras. Since you want to estimate all cameras' parameters, it is more convenient to minimize all reprojection errors, because it is able to fit the parameters better, since it provides lets say customize error for all cameras separately.