The motion of an electron traversing the intense coherent electromagnetic field in the focal region of anf/0.5 aplanatic lens is calculated for the purpose of studying charged‐particle acceleration. The results are compared with two simplified plane‐wave models for this interaction. This comparison emphasizes the need to consider longitudinal field components and three‐dimensional spatial modulation that are absent in simple models. Plane‐wave results overestimate the electron energy gain by an order of magnitude.