Section 11.2.6.7.2. Elimination of peak pixel outliers

In the same way that outliers in the background region can be identified and rejected (see Section 11.2.5.1.1), it is possible in principle to identify outliers in the peak region of fully recorded reflections as those pixels whose deviation from the scaled standard profile is significantly greater than that expected from counting statistics. This approach works well if the feature that gives rise to the outliers affects only a small fraction of the peak pixels and gives rise to large deviations, and this is the case for some zingers or dead pixels, and for diffraction from small ice crystals when collecting data from cryo-cooled samples.

Another source of outliers is the encroachment of a strong neighbouring spot into the peak region, as discussed in Section 11.2.6.7.1. When dealing with peripheral pixels, the outlier test can be applied to both fully recorded and partially recorded reflections, but a high σ cutoff (e.g. 10–20) must be used to avoid rejecting pixels that do not fit the profile simply because they correspond to a partially recorded spot.