Source: https://guthlabs.ai/docs/instruments/field-of-view-calculator-sensor-focal-length/implementation/

instrument implementation / implementation-contract

# Field of View Calculator (Sensor + Focal Length) implementation

A source-bound implementation contract for Field of View Calculator (Sensor + Focal Length); 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**: t4-181

**Effect**: Computation or source lookup only

## Input and validation requirements

The zero-diagonal input causes the equivalent-focal-length calculation to divide by zero. The zero-width boundary also produces mathematically finite but physically invalid output, and a negative focal length yields signed negative AOVs unless explicitly rejected or normalized.

## 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": {
    "sensor_width_mm": 36,
    "sensor_height_mm": 24,
    "focal_length_mm": 50
  },
  "expected_outputs": {
    "horizontal_aov_deg": 39.6,
    "vertical_aov_deg": 26.99,
    "diagonal_aov_deg": 46.79,
    "equivalent_focal_length_mm": 50.04
  },
  "working": "Diagonal=sqrt(36^2+24^2)=sqrt(1872)=43.2666 mm. Horizontal=2*atan(36/(2*50))*180/pi=2*atan(0.36)*180/pi=2*0.34556*57.2958=39.60 degrees. Vertical=2*atan(24/100)*180/pi=2*atan(0.24)*57.2958=2*0.23554*57.2958=26.99 degrees. Diagonal=2*atan(43.2666/100)*57.2958=2*atan(0.432666)*57.2958=46.79 degrees. Equivalent=50*(43.3/43.2666)=50.04 mm."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/field-of-view-calculator-sensor-focal-length/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/field-of-view-calculator-sensor-focal-length/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/field-of-view-calculator-sensor-focal-length/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-tranche4/tranche4-results.json`