Source: https://guthlabs.ai/docs/instruments/sunny-16-exposure-rule-of-thumb-panel/implementation/

instrument implementation / implementation-contract

# Sunny 16 / Exposure Rule-of-Thumb Panel implementation

A source-bound implementation contract for Sunny 16 / Exposure Rule-of-Thumb Panel; 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**: t7-075

**Effect**: Computation or source lookup only

## Input and validation requirements

The specification does not define validation behavior for ISO=0, which produces an undefined result, and it does not provide authoritative stop values or a sign convention for the backlit preset. A panel that accepts ISO=0 or silently chooses a backlit convention can return invalid or non-reproducible outputs.

## 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": {
    "lighting_condition": "full sun",
    "ISO": 100,
    "desired_aperture_f": 16
  },
  "expected_outputs": {
    "suggested_shutter_speed_seconds": 0.01,
    "suggested_shutter_speed_reciprocal": 100
  },
  "reference_data": {
    "sunny16_baseline": {
      "aperture_f": 16,
      "shutter_seconds_at_ISO_1": 1,
      "source_convention": "widely tabulated standard value"
    },
    "lighting_preset": {
      "name": "full sun",
      "adjustment_stops": 0,
      "source_convention": "widely tabulated standard value"
    }
  },
  "working": "Sunny 16 baseline: t = 1 / ISO = 1 / 100 = 0.01 s. Aperture correction: (16 / 16)^2 = 1. Therefore t = 0.01 × 1 × 2^0 = 0.01 s = 1/100 s."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/sunny-16-exposure-rule-of-thumb-panel/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/sunny-16-exposure-rule-of-thumb-panel/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/sunny-16-exposure-rule-of-thumb-panel/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`