ISO after stops change calculator
Photographic ISO is a logarithmic sensitivity scale: each full stop doubles or halves how much light the sensor or film needs for a given aperture and shutter.
Run — free
When you already know the starting ISO and you only want the new number after raising or lowering the dial by a given number of stops, the closed form is ISO two equals ISO one times two to the power of the signed stop change. Positive stops raise sensitivity and usually add noise; negative stops lower sensitivity and usually clean the file. Fractional thirds such as plus one third or minus two thirds follow the same power of two, which is why one third of a stop from ISO one hundred lands near the familiar one hundred twenty-five label. This ISO after stops change calculator accepts a starting ISO and a signed stop delta, returns the exact product, a camera-style integer ISO, the nearest standard one-third-stop label from the common photographic scale, the linear multiplier two to the power of the delta, and a raise-or-lower-or-unchanged direction. The path is pure deterministic arithmetic with no network, no random seeds, and no wall-clock dependence, so the free browser runner and the prepaid API return the same JSON after fixed rounding every time you call it.
How to use it
Enter your values in the form above. The tool checks them before calculating and shows the result on the same page.
Check your inputs
Use the labels and units shown next to each field. If something is missing or outside the allowed range, the page points to the field to fix.
Use it again or automate it
Use the browser tool for individual checks and the API when you need the same capability in an automated workflow.
What you can do with it
Get an answer now
Enter one set of values and see the result without building a spreadsheet or script.
Compare scenarios
Change one value at a time and rerun the calculation to understand what affects the result.
Automate repeated work
Use the API when the same calculation needs to run inside your product or workflow.
FAQ
How do I use this capability?
Complete the fields above and run it on this page. The form highlights anything that needs attention.
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/hobby/photo-iso-after-stops \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"iso":100,"stops":2}'const res = await fetch("https://api.kit.forhosting.com/hobby/photo-iso-after-stops", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"iso": 100,
"stops": 2
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/hobby/photo-iso-after-stops",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"iso": 100,
"stops": 2
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/hobby/photo-iso-after-stops", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"iso":100,"stops":2}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"iso":100,"stops":2}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/hobby/photo-iso-after-stops", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"iso": 100,
"stops": 2
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "hobby.photo_iso_after_stops",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |