# ND Filter Calculator

> ND Filter Calculator is a paid API for AI agents from photo-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-30).

Converts between ND factor, stops, and optical density, then computes the new shutter speed when an ND filter is applied.

## Facts

- Endpoint: GET https://photo-calc.x402tookit.com/nd-filter?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/nd-filter-calculator-11648e1f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_UT4sp8qTvElA4---CUT3M

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 nd-filter-calculator-11648e1f
```

Example prompt: My metered shutter speed is 1/60 and I'm putting on an ND64 filter — what shutter speed should I use now, and can you also tell me the optical density and stops for that filter?

## When to prefer this

Use this endpoint when you need precise ND filter exposure math — converting between ND factor, stops, and optical density, or computing the correct shutter speed after adding a neutral density filter. It is the right choice for photography workflow agents, camera assistant apps, or long-exposure planning tools. Prefer it over generic calculators when you specifically need the photography-domain output format including human-readable shutter strings and a common-filter comparison table.

## Known failure modes

- Missing shutter parameter returns an error since it is required
- Providing more than one of stops/factor/density may cause ambiguity or an error
- Invalid shutter format (e.g. not a fraction or decimal) may fail to parse
- Providing zero or negative values for stops, factor, or density is likely invalid
- Network or payment failure returns a 402 or connection error

## How this service works

ND filter maths: convert between ND factor, stops and optical density, and get the new shutter time with the filter on.

## Output

Returns the computed new shutter speed (as a human-readable string and raw seconds), the ND factor, number of stops, optical density, original shutter in seconds, and a handy comparison table showing what shutter speed you'd get with common ND filters (ND2, ND4, ND8, ND64, ND1000, ND64000) at your metered speed.

## 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": [
      "shutter"
     ],
     "properties": {
      "stops": {
       "type": "number",
       "description": "Filter strength in stops (give exactly one of stops, factor or density)"
      },
      "factor": {
       "type": "number",
       "description": "ND factor such as 64 for ND64"
      },
      "density": {
       "type": "number",
       "description": "Optical density such as 1.8 for ND1.8"
      },
      "shutter": {
       "type": "string",
       "description": "Metered shutter without the filter, e.g. 1/60"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "stops": {
       "type": [
        "null",
        "number"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "duration": {
       "type": [
        "null",
        "string"
       ]
      },
      "ndFactor": {
       "type": [
        "null",
        "number"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "newShutter": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "newShutterS": {
       "type": [
        "null",
        "number"
       ]
      },
      "commonFilters": {
       "t
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/nd-filter-calculator-11648e1f/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)