The per-frame scale is smoothed over the rotation inside both scaling loops, which is what stopped a
fine-sliced sweep of a small cell from walking its own scales down fifteen decades. But the window is
a prior about the dose and the crystal, and on a merge where one frame carries hundreds of
observations the frame's own data outvote it. Smoothing them anyway does not remove the per-frame
structure, it moves it into the error model: on a 360 degree merge at 14x multiplicity the scale the
window averaged away is 2.2% rms, which is most of the 2.4% of unmodelled error the change added
there, and it cost ISa 29.0 -> 23.8 and 43.3 -> 38.0 on two long high-multiplicity protein sweeps.
So the loop over the fulls now ends with one free fit against the settled reference, shrunk frame by
frame back toward the restrained scale by how much of the difference is real. Real and noise separate
with nothing to tune, because a rocking event spans several frames and the fit's noise does not:
whatever moved a frame's scale moved its neighbour's, so the lag-1 covariance of the difference is
the systematic's variance and what is left of the total is the fit's. A sweep that measures its
scales to a fraction of a percent keeps nearly all of what it measured; one sliced at a twentieth of
its rocking curve, where a frame holds twenty-five fulls and the difference has no correlation with
its neighbour at all, keeps none of it and is scaled exactly as before. Neither is told which it is.
Only the fulls, and only off a settled loop. A partial's scale is the direction the collapse runs in
and handing any of it back re-opens it - shrunk or not, it costs ISa 23.8 -> 14.8 on the same merge
and takes a small-cell monoclinic set from 14.2 to 2.7 - while a full is a whole rocking event and
cannot enter it; and a loop that walked until it was stopped has measured nothing to hand back.
Measured against the current behaviour. Two long high-multiplicity protein sweeps: ISa 23.8 -> 27.0
and 38.0 -> 41.3, with R_meas and the anomalous signal moving with them (SigAno 0.929 -> 0.949,
CC_anom 0.18 -> 0.22 on the first). A long-wavelength, high-multiplicity series collected at three
goniometer settings - the case the restraint is right for, sliced twenty times finer than its rocking
curve: ISa 13.7 -> 13.9, 14.2 -> 14.6, 12.5 -> 12.8, SigAno up on all three, and the anomalous peak
heights at the deposited model's own sites unchanged to a tenth of a sigma. The fine-sliced, small-cell
and powder sets the restraint was added for are unchanged to the last reported digit, as are the
short-sweep tetragonal pair and every space group.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013nW6FNRP1bBJJ8pfHiByAT
leonarski_fandClaude Opus 5
a970e5223b