To the best of our knowledge, the Λ metric has only ever been evaluated using canonical MOs (CMOs), but since Λ does not respect orbital invariance this choice is arbitrary. Nevertheless, the value Λ CMO in the CMO representation does provide a useful (albeit functionalspecific) threshold, beyond which TD-DFT excitation energies should not be taken seriously unless range separation is used. For interpretative purposes, a drawback of this dimensionless metric is that it does not quantify electron-hole separation in a way that is readily visualizable.