Flash Guide Number Calculator mechanism

Model scope

The core relationship is correct under the stated unit and ISO assumptions. The spec needs an explicit ISO reference for the input GN—normally ISO 100—and explicit same-unit validation before it can receive PASS. The honest label that manufacturer GN ratings are approximate or optimistic should remain visible.

• The GN=aperture*distance relationship is standard, but the stated formulas omit the ISO adjustment; the implementation must explicitly define whether the entered GN is rated at ISO 100 and calculate GN_effective=GN_input*sqrt(ISO/100).
• The spec does not explicitly state that guide number and distance must use the same unit system, such as both meters or both feet.

Units and conventions

• Guide number and distance use identical units; GN in meters requires distance in meters, and GN in feet requires distance in feet.
• The entered guide number is assumed to be the manufacturer rating at ISO 100.
• ISO scaling uses GN_effective=GN_ISO100*sqrt(ISO/100).
• Aperture is an f-number and is dimensionless for this calculation.
• ISO is a positive numeric sensitivity value.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "operation": "aperture",
    "guide_number": 36,
    "guide_number_unit": "m",
    "iso": 100,
    "distance": 6,
    "distance_unit": "m"
  },
  "expected_outputs": {
    "aperture": 6,
    "effective_guide_number": 36
  },
  "working": "ISO factor=sqrt(100/100)=1. Effective GN=36*1=36 m. Aperture=effective GN/distance=36/6=6, so the required aperture is f/6."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

Zero distance produces an undefined aperture and would yield Infinity in unvalidated plain JavaScript arithmetic; negative distance also exposes a sign-convention hazard that can produce a nonsensical negative aperture.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche4/tranche4-results.json
• BOUNDARY_HAZARD_CATALOG.json