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

ABSTRA C T We present here an alternative method for calculating magnifications in gravitational lensing calculations ‐ the ray-bundle method. We provide a detailed comparison of the distribution of magnifications obtained by this method with those obtained through analytic results and conventional ray-shooting methods. The ray-bundle method provides high accuracy in the weak lensing limit, and is computationally much faster than (non-hierarchical) ray-shooting methods of a comparable accuracy. The ray-bundle method is a powerful and efficient technique with which to study gravitational lensing within realistic cosmological models, particularly in the weak lensing limit.