# Exposure Match Calculator

A tiny static web app that calculates equivalent camera exposure settings between a **reference camera (A)** and a **target camera (B)**.

## How it works

The app uses exposure equivalence:

`(N² / t) × (100 / ISO) = constant`

Equivalent rearranged form:

`t₂ = t₁ × (N₂² / N₁²) × (ISO₁ / ISO₂)`

Where:

- `N` = f-number (aperture)
- `t` = shutter time in seconds
- `ISO` = sensor sensitivity value

## Usage

1. Open the app in your browser.
2. Fill all values for **Camera A (reference)**.
3. In **Camera B (target)**, enter exactly two values and leave one empty.
4. Click **Calculate Missing Value**.
5. The app computes the missing target value for equal exposure.

## Run locally

No build tools required.

- Clone the repository.
- Either:
  - Open `index.html` in your browser.
  - Or start a http server inside the repo directory, e.g. with:
    
    ```sh 
      python -m http.server
    ```
  
    and navigate to `localhost:8000` in your browser.

## License (GPLv3)

This project is licensed under the **GNU General Public License v3.0** (GPL-3.0).  
You are free to use, modify, and redistribute this software under the terms of that license.  
If you distribute modified versions, you must also provide the source code and keep it under GPLv3.

See the [LICENSE](LICENSE) file for the full license text.

## Notes

- Shutter input supports values like `1/250`, `0.004`, or `2`.
- Calculator is for technical equivalence; real-world image differences (noise, lens transmission, dynamic range) still apply.