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leonarski_fandClaude Opus 5 49dd01331b calibration: let the spots vote on the geometry in ring mode too

The rings and the spots fail in different regimes, which is the whole reason to
carry both. The header is right on a well-configured instrument and is the thing
a calibration is run to check. The profile's own estimates are exact while the
error stays small and stop meaning anything beyond that - past about half a ring
spacing each ring reaches the azimuthally averaged profile as two horns rather
than one peak, and the distance search reads a list of horns as a list of rings.
The circle through the spots reads nothing from the header at all: measured on a
110 mm LaB6 exposure, --calibration spots returns the same geometry from a header
400 px out in the centre AND eight times out in distance.

So ring mode now finds spots as well - half a second - and offers what they make
of the geometry as one more starting hypothesis, fitted like the others with the
residual left to choose. It is added whole rather than as a centre alone:
GuessGeometry votes for the circle centre, clusters the radii into rings and
takes the distance from the innermost, and those two belong together. Taking only
its centre would not have helped, because the distance candidates come from a
profile averaged about the header's centre, and a ring smeared over hundreds of
pixels cannot be un-smeared by reading its bins differently.

Measured on the 110 mm exposure, whose true PONI is 765.90 at 110.03 mm. A header
40 px out in the centre now lands within 0.6 px (it landed 41 px away before).
The cases with BOTH wrong, which failed before this and equally before the beam
centre work, now come out: 250 mm / 780 px gives 110.041 mm and 766.10 px against
42.3 mm and 782.7; 250 mm / 867 px gives 110.065 and 765.48. All five datasets
are unchanged from their correct headers and the distance still recovers from any
header between 25 and 1200 mm.

Past about a hundred pixels nothing rescues ring mode, and the reason is the
profile rather than the seeding: binned about a centre that far out it shows each
ring smeared across its own sectors, so even started from the exact answer the
fit leaves rms 4.8 px and drifts. Re-binning would fix it and would need the
images read a second time; --calibration spots, which never touches the profile,
already covers it.

That regime is now visible rather than silent. The spots' beam centre is printed
beside the fitted one as a cross-check - two methods sharing no assumption, so a
reader can see at a glance whether they agree. It costs nothing, the spots having
been found already, and it separates cleanly: 0.3-0.4 px on the good runs against
201.4 px on the exposure whose profile could not be fitted at all. Reported as a
fact and not gated on, since at long distance both methods weaken together and
the honest thing is to show the number (5.2 px at 300 mm, 12.6 at 500).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NfuDvf5ipV3Hi8TiCUKD27

2026-08-31 17:58:26 +02:00