LEED intensity curves between 0–50 eV contain sharp peaks due to electronic surface resonances. Successful comparison with theory requires an accurate knowledge of the incidence angles and energy resolution ≲0.15 eV. It is shown that these requirements can be achieved with a conventional LEED system. The resolution was obtained by doubly modulating the four grid retarding optics and the electron gun. The incidence angles were found with a simple photographic technique.