Exposure Trade

{
  "after": {
    "aperture": 11,
    "iso": 100,
    "nearestStandardAperture": 11,
    "shutter": "1/32 s",
    "shutterS": 0.030867347
  },
  "asOf": "2026-10-11T08:40:14.514Z",
  "before": {
    "aperture": 5.6,
    "iso": 100,
    "shutterS": 0.008
  },
  "changed": "newAperture",
  "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.",
  "notChecked": [
    "the lens' actual aperture range and the camera's shutter limits",
    "image-quality trade-offs: noise at high ISO, diffraction at small apertures, motion blur at slow shutters",
    "…1 more"
  ],
  "reasons": [
    "A stop is a doubling or halving of light: shutter time x2, ISO x2, or aperture area x2 (f-number x 1.414).",
    "Standard stops: f/1.4 2 2.8 4 5.6 8 11 16 22."
  ],
  "source": "computed locally",
  "stopsChanged": -1.948,
  "summary": "aperture changed by -1.95 stop(s) of light; shutter compensates to 1/32 s at the same ISO: f/11, 1/32 s, ISO 100 matches f/5.6, 1/125 s, ISO 100.",
  "verdict": "EQUIVALENT_EXPOSURE"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://photo-calc.x402tookit.com/exposure-trade?aperture=5.6&iso=100&newAperture=11&shutter=1%2F125'

# 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/exposure-trade?aperture=5.6&iso=100&newAperture=11&shutter=1%2F125' \
  | 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%2Fexposure-trade
const res = await pay("https://photo-calc.x402tookit.com/exposure-trade?aperture=5.6&iso=100&newAperture=11&shutter=1%2F125");
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/exposure-trade?aperture=5.6&iso=100&newAperture=11&shutter=1%2F125")
    print(res.status_code, res.text)