Data quality statistics for crystals of Zn-free insulin as calculated by SHELXC. (a) Anomalous signal-to-noise d′′/sig as a function of resolution. Statistics for data collected at 13 keV are shown in red, for data collected at 4 keV without and with 2Θ-offset in blue and green, respectively, for the combination of the two 4 keV data sets in black. (b) Multiplicity as a function of resolution. Colour codes are the same as in panel (a).