Nd Filter

{
  "asOf": "2026-10-11T08:40:15.565Z",
  "commonFilters": {
    "ND1000": "~10",
    "ND2": "1 stop",
    "ND4": "2",
    "ND64": "6",
    "ND64000": "~16",
    "ND8": "3"
  },
  "degraded": false,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "duration": "17 s",
  "ndFactor": 1024,
  "newShutter": "17.1 s",
  "newShutterS": 17.066667,
  "notChecked": [
    "reciprocity failure on film (long exposures need extra time)",
    "colour casts and IR leakage of strong filters",
    "…1 more"
  ],
  "opticalDensity": 3.0103,
  "originalShutterS": 0.016666667,
  "reasons": [
    "Each stop doubles the exposure time: new time = old time x 2^stops. Optical density = stops x 0.301.",
    "Within a normal camera shutter range."
  ],
  "source": "computed locally",
  "stops": 10,
  "summary": "10 stops = ND1024 = density 3.01: 1/60 s becomes 17.1 s.",
  "verdict": "LONG_EXPOSURE"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://photo-calc.x402tookit.com/nd-filter?shutter=1%2F60&stops=10'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://photo-calc.x402tookit.com/nd-filter?shutter=1%2F60&stops=10' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fphoto-calc.x402tookit.com%2Fnd-filter
const res = await pay("https://photo-calc.x402tookit.com/nd-filter?shutter=1%2F60&stops=10");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://photo-calc.x402tookit.com/nd-filter?shutter=1%2F60&stops=10")
    print(res.status_code, res.text)