The concept of a spatial frequency‐dependent, detective quantum efficiency [=DQE( f )] is applied to the performance assessment of a prototype parallel detection system for electron energy‐loss spectrometry. The various factors which determine DQE( f ) in such a system are discussed and comparisons are made with a serial detection system. Also, the effects of the electron source energy spread on the overall spectrometer DQE( f ) are discussed. In these examples, the clear importance of including the spatial frequency dependence of DQE is demonstrated.