Figure 3 Result of a MEM calculation simulating the single-crystal case of the new A-constraints (compare with Fig. 2). Only one strong reflection (114) was used as the F-constraint, first with the correct sign (a) and in a second calculation with the wrong sign (b). The remaining 69 reflections were used as A-constraints, i.e. with ambiguity in their phase (1 F-constraint, 69 A-constraints).