Comparison of the phase quality obtained for the HMT-derivative DR6 crystals. The cosine of the phase error between the experimental protein phases and the final model phases is shown as function of the resolution (see §2 for details). Filled triangles represent phases calculated by spherical averaging in SHARP (SPHCLUSTER option), whereas open symbols represent phases calculated from the individual tungsten positions of the MR searches calculated at 2.9 Å resolution (squares) and 4.4 Å resolution (circles). The resolution limits refer to the data used for the heavy-atom cluster orientation by MR; the final phases were always calculated up to the resolution maximum of the data sets (Table 1). Phases calculated from the respective heavy-atom models are connected by solid lines; phases after density modification are connected by broken lines. (a) Comparison of phases determined in a three-wavelength MAD experiment. (b) Comparison of phases determined by a SIRAS experiment.