\centerline{attention: seminar canceled} (Weak values of quantum operators occur when quantum measurements are both pre- and post-selected. They are characterized by the peculiar features of both being complex and exceeding the eigenvalue bound of the operator. \par We show how this quantity may be described in a theoretically consistent way by defining contextual values as a generalization of the eigenvalues of an observable that takes into account both the system observable and a general measurement procedure. We further give examples in the solid state and in optical systems showing how weak values may be used as a novel amplification scheme for precision measurements.) \\ \\ \\ \centerline{(attention: UNUSUAL DAY,} \\ \centerline{organizer: Cristina Bena)}