counting op• Data kinds: image2d → table
• Call: import fullseye as fs; fs.ledger.photon_statistics(counts) (to call the implementation directly, import photoncount; photoncount.photon_statistics(counts); from the registry, opsphoton.get("photon_statistics"))
Poisson statistics of a photon-count frame: is it really shot-noise limited?
Returns a dict: mean · variance (population, ddof=0) · fano_factor = variance / mean (1 for a Poisson process) · snr_poisson = sqrt(mean) (the theoretical photon-limited SNR) · snr_measured = mean / std (what this frame actually achieved) · total_counts · n_samples · zero_fraction (the fraction of pixels that saw no photon at all — the honest measure of "photon starved"; exp(-lambda) for a flat field) · max_counts.
The Fano factor is evidence of Poisson statistics only on a flat field. On a structured scene the scene's own spatial variance dominates and the ratio is large and meaningless — this op computes the number, it cannot tell you which situation you are in. Measured on the test scenes: a flat lambda = 100 field (512x512, seed 0) gives 1.001089; the same detector looking at a linear ramp from 20 to 180 photons gives 22.4102. Both are "correct" and only one of them means anything.
Raises ValueError: negative, non-finite or non-2-D *counts*, fewer than 2 pixels (no variance), an all-zero frame (fano_factor would be 0/0 — say "no photons were detected" instead of returning NaN), and a frame with exactly zero variance (snr_measured would be inf; for n >= 2 a constant frame is not a Poisson realisation but a synthetic constant, i.e. an input mistake).
• photon_timeresolved family guide
• Sample-data catalog (download URLs / licences) — 2-D uses skimage.data (BSD/public domain) plus synthetic images; 3-D lists download URLs for real data sources (Stanford, PDS, …).
• Operator provenance and references — the sources of the research/methods this op family came from.
• The canonical algorithm (author, year) and its uses are named in the family usage guide above.
• photon_timeresolved — py -3.11 examples/photon_timeresolved.py
table as input)—
counting)photon_sample · photon_uncertainty
*Provenance: photoncount.py — PHOTON operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.