Crop Factor

{
  "asOf": "2026-10-11T08:40:13.999Z",
  "cropFactor": 1.999,
  "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.",
  "equivalentAperture": 3.599,
  "equivalentFocalMm": 49.985,
  "equivalentIso": 1599,
  "notChecked": [
    "real exposure: equivalent aperture describes depth of field and noise, not the light the lens delivers (f/1.8 is still f/1.8 for exposure)",
    "differences in aspect ratio between sensors (the diagonal is used)",
    "…1 more"
  ],
  "reasons": [
    "Crop factor = full-frame diagonal (43.27 mm) / sensor diagonal. Equivalent focal length and aperture both multiply by it; equivalent ISO by its square.",
    "Equivalence compares framing, depth of field and noise: the exposure (shutter speed at a given f-stop and ISO) does not change."
  ],
  "sensor": "micro-four-thirds",
  "sensorAreaRelativeToFullFramePct": 26.03,
  "sensorMm": {
    "diagonal": 21.64,
    "height": 13,
    "width": 17.3
  },
  "source": "computed locally",
  "summary": "Micro Four Thirds 17.3 x 13 mm: crop factor 2; 25 mm acts like 49.98 mm on full frame; f/1.8 gives the depth of field of f/3.6; ISO 400 has the noise of about ISO 1599.",
  "verdict": "COMPUTED"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://photo-calc.x402tookit.com/crop-factor?aperture=1.8&focalMm=25&iso=400&sensor=micro-four-thirds'

# 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/crop-factor?aperture=1.8&focalMm=25&iso=400&sensor=micro-four-thirds' \
  | 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%2Fcrop-factor
const res = await pay("https://photo-calc.x402tookit.com/crop-factor?aperture=1.8&focalMm=25&iso=400&sensor=micro-four-thirds");
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/crop-factor?aperture=1.8&focalMm=25&iso=400&sensor=micro-four-thirds")
    print(res.status_code, res.text)