An edge phantom for assessing the sharpness response of a radiation image recording and detection system wherein the edge phantom is subjected to radiation emitted by a source of radiation to generate a radiation image and wherein the radiation image, recorded and detected by the system, is evaluated. The design of the edge phantom provides that any line outside a plane perpendicular to the edge phantom's top face, connecting the focus of the source of radiation with a point on a curved or flat lateral face of the phantom used for sharpness analysis coincides with a line part of that lateral face containing that point.