Instrumental resolution, i.e. resolution in reciprocal space from components upstream of the sample position. The red line shows the expected rocking-curve width from a Si single crystal irradiated by the full beam. Experimentally observed rocking widths for one to three (h,h,h) reflections in Bragg geometry (crosses) and Laue geometry (circles), respectively, are in good accordance with the expected values. XRPD data were obtained with an apertured beam leading to the instrumental resolution represented by the blue line.