# Photography Calculators – Sunny-16 Rule

> Photography Calculators – Sunny-16 Rule is a paid API for AI agents from photo-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-29).

Returns starting aperture, shutter speed, and exposure value for a given weather condition and ISO using the Sunny-16 rule, plus equivalent exposure combinations.

## Facts

- Endpoint: GET https://photo-calc.x402tookit.com/sunny-16?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/photography-calculators-sunny-16-rule-42e74f33
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_x1FwKd1lLzmGKRuBu4rzq

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability photography-calculators-sunny-16-rule-42e74f33
```

Example prompt: Using the sunny-16 rule, what aperture and shutter speed should I start with for a slightly overcast day shooting at ISO 400?

## When to prefer this

Choose this endpoint when you need a quick, rule-based starting exposure for outdoor natural-light photography without a light meter, especially for film photographers or anyone unfamiliar with metering. It is ideal for coaching users on the sunny-16 rule rather than computing a precise light measurement.

## Known failure modes

- Missing required 'weather' query parameter returns an error
- Invalid weather enum value (e.g. 'foggy') causes a validation error
- Very high or unusual ISO values may yield unexpected results
- Network timeout or upstream service unavailability

## How this service works

The sunny-16 rule: starting aperture and shutter speed for sun, cloud or shade at your ISO, with the exposure value it implies.

## Output

Returns the recommended aperture (f-number), shutter speed (as a fraction string and decimal seconds), ISO used, EV100 value, a plain-English summary of the lighting level, a list of equivalent exposure combinations (different aperture/shutter pairs at the same EV), weather condition echoed back, and a disclaimer about the rule being a starting point.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "weather"
     ],
     "properties": {
      "iso": {
       "type": "number",
       "description": "ISO or film speed (default 100)"
      },
      "weather": {
       "type": "string",
       "description": "snow-sand, sunny, slight-overcast, overcast, heavy-overcast or open-shade"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "iso": {
       "type": [
        "null",
        "number"
       ]
      },
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "ev100": {
       "type": [
        "null",
        "number"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "shutter": {
       "type": [
        "null",
        "string"
       ]
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "weather": {
       "type": [
        "null",
        "string"
       ]
      },
      "aperture": {
       "type": [
        "null",
        "number"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "shutterS": {
       "type": [
        "null",
        "number"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "description": {
       "type": [
        "null",
        "string"
       ]
      },
      "equivalents": {
       "type": [
        "array",
        "null"
       ],
       "items": {
  
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/photography-calculators-sunny-16-rule-42e74f33/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from photo-calc.x402tookit.com](https://www.zero.xyz/host/photo-calc.x402tookit.com/llms.txt)