Ice-ring reflections are flagged and "excluded from scaling, kept for merging",
but ApplyCellSurface never read the flag. While the fit dropped Is <= 0 this was
mostly hidden: the over-subtracted half of the on-ring observations went with the
filter. Once the negatives were admitted (1d1a40d90), a set with strong, azimuthally
uneven rings fitted its surfaces to the rings: with the surfaces off the error
model's b is 0.018, and the surfaces no longer took it down.
On the two in-house lysozyme sets with heavy ice (25% of reflections flagged):
ISa 7.57 -> 10.08 and 7.08 -> 10.16, b 0.0155 -> 0.0090; on a third, 3.57 -> 4.37
(4.41 before the filter was removed). A run where no ice is detected sets no flag
and is unchanged. The remaining gap to the filtered surfaces (ISa ~15) and to
XDS (~20) is not ice: extending the flag to the measured powder rings moved
nothing, and a symmetric residual cut and a variance rebuilt at the reference did
not either.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013nW6FNRP1bBJJ8pfHiByAT
leonarski_fandClaude Opus 5
d5f7e95d41