A selectively configurable system for directing an electron beam with a limited energy spread to a sample includes an electron source to generate an electron beam having an energy spread including one or more energies, an aperture having an on-axis opening and an off-axis opening, a first assembly of one or more electron lenses with selectively configurable focal powers positioned to collect the beam from the source and direct the beam to the aperture, a second assembly of one or more selectively configurable electron lenses positioned to collect the beam, a sample stage, and an electron inspection sub-system including electron optics positioned to direct the beam onto one or more samples. The first assembly includes an off-axis electron lens for interacting with the beam at an off-axis position and introducing spatial dispersion to the beam when configured with a nonzero focal power, thus filtering the energy spread.