The ray-bundle method for calculating weak magnification by gravitational lenses

We present here an alternative method for calculating magnifications in gra vitational lensing calculations - the ray-bundle method. We provide a detai led comparison of the distribution of magnifications obtained by this metho d with those obtained through analytic results and conventional ray-shootin g methods. The ray-bundle method provides high accuracy in the weak lensing limit, and is computationally much faster than (non-hierarchical) ray-shoo ting methods of a comparable accuracy. The ray-bundle method is a powerful and efficient technique with which to s tudy gravitational lensing within realistic cosmological models, particular ly in the weak lensing limit.