1. An edge phantom for assessing the sharpness of a radiation image recording and detection system wherein said edge phantom is subjected to radiation emitted by a source of radiation to generate a radiation image of said phantom and wherein a digital image representation corresponding with said radiation image is generated and evaluated, characterized in that any line, outside a plane perpendicular to the top face of the edge phantom, connecting the focus of said source of radiation with a point on a curved or flat lateral face, used for sharpness analysis, of said phantom coincides with a line part of the lateral face containing said point.