Source: https://guthlabs.ai/docs/instruments/exposure-value-ev-to-lux-foot-candle-converter/implementation/

instrument implementation / implementation-contract

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

A source-bound implementation contract for Exposure Value (EV) to Lux/Foot-candle Converter; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## 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

[01**Overview**](<https://guthlabs.ai/docs/instruments/exposure-value-ev-to-lux-foot-candle-converter/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/exposure-value-ev-to-lux-foot-candle-converter/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/exposure-value-ev-to-lux-foot-candle-converter/qualification/>)

## 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`