Table 1.

Internal phase residuals of all possible two-sided plane groups using a representative image.

Two-sided plane group	Phase residual (degrees)a	Number of comparisons	Target residual (degrees)b
p1	27.8c	434
p2	40.8d	217	40.8
p12_b	73.7	113	29.3
p12_a	74.0	111	29.0
p121_b	76.6	113	29.3
p121_a	72.4	111	29.0
c12_b	73.7	113	29.3
c12_a	74.0	111	29.0
p222	59.0	441	34.2
p2221_b	58.4	441	34.2
p2221_a	62.2	441	34.2
p22121	69.3	441	34.2
c222	59.0	441	34.2
p4	30.0d	525	33.2
p422	51.3	998	30.6
p4212	61.6	998	30.6

Internal phase residuals were determined using the program ALLSPACE (Valpuesta et al., 1994) from spots of IQ1 to IQ5 to 7 Å resolution. Only plane groups compatible with the sbpA lattice are shown.

^aPhase residual versus other spots (90° random).

^bTarget residual based on statistics taking Friedel weight into account.

^cNote that in space group p1 no phase comparison is possible, so the numbers given here are theoretical phase residuals based on the signal-to-noise ratio of the observed diffraction spots.

^dWithin 20% of target residual.