Source: https://guthlabs.ai/docs/instruments/reciprocity-failure-calculator-film/implementation/

instrument implementation / implementation-contract

# Reciprocity Failure Calculator (Film) implementation

A source-bound implementation contract for Reciprocity Failure Calculator (Film); 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**: t7-030

**Effect**: Computation or source lookup only

## Input and validation requirements

The calculator must reject negative metered times when using a fractional exponent such as 1.3 because the real-valued result is undefined. It also has a significant unit-convention hazard: applying the power to an unnormalized numeric time makes seconds and minutes produce different physical results.

## 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": {
    "metered_time": 1,
    "time_unit": "s",
    "exponent_p": 1.3,
    "film_stock": "manual exponent"
  },
  "expected_outputs": {
    "corrected_time_s": 1
  },
  "reference_data": {
    "time_reference_s": 1,
    "source_convention": "widely tabulated standard value (SI): one second equals one second",
    "exponent_p": 1.3,
    "source_convention_exponent": "user-supplied manual exponent; not a manufacturer table value"
  },
  "working": "correctedTime = meteredTime^p\n= 1^1.3\n= 1 s.\nThis is an exact boundary case and lands on the widely memorized 1-second SI time entry."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/reciprocity-failure-calculator-film/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/reciprocity-failure-calculator-film/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/reciprocity-failure-calculator-film/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-tranche7/tranche7-results.json`