The value of _diffrn_detector_element.center[2] is the Y component of the distortion-corrected beam centre in millimetres from the (0, 0) (lower-left) corner of the detector element viewed from the sample side. The X and Y axes are the laboratory coordinate system coordinates defined in the AXIS category measured when all positioning axes for the detector are at their zero settings. If the resulting X or Y axis is then orthogonal to the detector, the Z axis is used instead of the orthogonal axis. Because of ambiguity about the setting used to determine this centre, use of this data item is deprecated. The data item _diffrn_data_frame.center_slow which is referenced to the detector coordinate system and not directly to the laboratory coordinate system should be used instead.