Employing a novel imaging mode based on the adjustment of a negative value of the spherical-aberration coefficient of the objective lens of a transmission electron microscope, we successfully imaged all types of atomic columns in the dielectric SrTi03 and the superconductor YBa2Cu307, in particular, the oxygen atoms [I]. This allowed us to detect local non-stoichiometries or the degree of oxygen-vacancy ordering. This technique offers interesting opportunities for research into the huge group of perovskite-derived electroceramic materials in which the local oxygen content sen-sitively controls the electronic properties.