Exposure Value (EV) to Lux/Foot-candle Converter implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t5-056

Effect

Computation or source lookup only

Input and validation requirements

• Reverse conversion is undefined for lux=0, fc=0, or any negative input because log2 requires a strictly positive argument.
• Very large positive EV values can overflow numeric implementations of 2^EV100; very small values can underflow.
• The API should reject negative lux and foot-candle inputs, and should require exactly one primary input mode unless consistency checking is explicitly implemented.
• The rounded factor 10.764 introduces small conversion error; use a documented precision consistently.
• A meter-calibration or incident-versus-reflected-light distinction is required to avoid implying that the estimate is a direct calibrated measurement.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "EV100": 0
  },
  "expected_outputs": {
    "lux": 2.5,
    "fc": 0.232255668
  },
  "working": "2^0=1. lux=2.5*1=2.5 lux. fc=2.5/10.764=0.232255668 fc."
}

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-tranche5/tranche5-results.json