Retrieval controller

Fixed token budget. Variable opening. Wide open = more sources, thinner signal. Stopped down = denser coherence, narrower depth of field. Diffraction zone: too closed, edge cases vanish.

Token budget C 32000

f-stop / aperture f/2.8

Wide open Stopped down Diffraction

Admitted sources

—

Signal density

—

Noise / contradiction risk

—

Depth of field

—

Recommended policy

—

Mapping: N ≈ f/D → admitted ≈ C · g(N); denser signal as N rises (tokens per source ↑).

Optional: Airy / diffraction note

In optics, the Airy disk angular radius scales ≈ 2.44 λ N (N = f-number). Here the same idea is a metaphor: past a sweet spot (~2 stops from wide open), further stopping-down shrinks the effective admission aperture until useful edge cases fall below the diffraction floor — not more “truth,” just less coverage. Formula caption is mnemonic, not a production ranking equation.