Automatic monitor brightness from real room light, measured with a colorimeter

A tiny Windows 11 tray app: your i1Display / ColorMunki sits next to the screen, measures the room in lux every 30 seconds, and AmbientLightCalibrate sets every monitor to the right brightness in nits over DDC/CI.

Why · Features · Install · How it works · Support · Українською

  

_{Tray flyout and settings (Ukrainian UI shown; the app is in English on non-Ukrainian Windows).}

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🤔 Why

Phones and laptops dim and brighten with the room; desktop monitors don't. Calibration tools such as Calibrite PROFILER can measure ambient light and suggest a brightness, but they don't keep adjusting it. AmbientLightCalibrate does — with real numbers instead of guesses:

• Measures, not estimates. Room light comes from your colorimeter's ambient diffuser (lux), and every monitor's brightness is mapped to measured luminance (nits), so two different monitors land on the same nits.
• Keeps your calibration. Only the backlight (DDC/CI VCP 0x10) is changed — never RGB gains, never the video LUT. White point and gamma of a calibrated LCD stay put.
• Quick and calm. A light switched on or off is followed within one reading, with a one-second fade; a dead zone keeps it from twitching. The sliders move live while it adjusts.
• Safe. Leaves a monitor alone while it is in HDR (HDR wants full backlight), and pauses while DisplayCAL, ArgyllCMS, HDRDisplayCalibrate, Calibrite/i1Profiler or similar tools are using the sensor.

✨ Features

Auto brightness	Room lux → target nits through an editable curve; a reading every 30 s (10 s minimum); big changes are confirmed by a second reading at once, then faded in
Per-monitor sliders in nits	Plus "all monitors" and presets 80 / 100 / 120 / 140 / 160 / 200
Curve offset	One slider to make the whole automation brighter or darker
Built-in brightness calibration	~1 min per monitor: AmbientLightCalibrate steps the backlight 0→100 and measures nits
Native look	Windows 11 dark Fluent flyout with acrylic backdrop, English / Ukrainian UI
Calibration reminder	Every 1 / 2 / 3 months (or off): reads the creation date of each monitor's active SDR and HDR colour profile, shows a banner and a tray notification, "remind me in a week"
Start with Windows	One switch (per-user Run key, no admin)
Log	Every reading and change, in %APPDATA%\AmbientLightCalibrate\log.txt

📋 Requirements

• Windows 10 or 11, monitors with DDC/CI enabled in their on-screen menu.
• A colorimeter with an ambient-light diffuser supported by ArgyllCMS: X-Rite/Calibrite i1Display Pro / ColorMunki Display / Display Plus, Datacolor Spyder X / 5 and others.
• ArgyllCMS installed (or DisplayCAL, which bundles it). AmbientLightCalibrate finds it in the usual places; otherwise set the folder in Settings.

📦 Install

1. Download AmbientLightCalibrate.exe from Releases — one self-contained file, no .NET install needed. Put it anywhere and run it; a sun icon appears in the tray.
2. Calibrate brightness once per monitor: tray icon → ⚙ Settings → Calibrate next to a monitor → hang the sensor in the centre of that screen with the diffuser open → Start. AmbientLightCalibrate measures brightness 0, 15, 30, 50, 70, 100 and restores your setting.
3. Place the sensor for ambient light: diffuser closed, near the screen, facing the room / your seat (a small tripod mount behind the monitor works; see Offset below).
4. Switch Auto brightness on. Done.

⚙️ How it works

 colorimeter (diffuser closed)                     every N seconds (default 30)
          │  spotread -a  →  room lux
          ▼
   curve: lux → nits  (+ offset)       2 lx → 100 · 10 lx → 120 · 50 lx → 140 · 150 lx → 160 · 400 lx → 185 · 1000 lx → 220
          │
          ▼  per monitor: measured map  Brightness → nits   (from the one-time calibration)
   DDC/CI  SetVCPFeature(0x10)          only if the change is above the dead zone; faded in over ~1 s

• Curve – editable in Settings. Defaults follow common viewing guidance: ~100–120 nits in a dim room, 160–220 nits in daylight.
• Offset – shifts the whole curve. Use it if the defaults feel dim, or when the sensor sits where it sees less light than the screen does (e.g. behind the monitor).
• A big jump is confirmed by a second reading right away: a lamp switched on reacts within one cycle, while someone walking past the sensor changes nothing. A dead zone (default 6 %) ignores small drifts, and the new brightness is faded in over about a second. An optional max step (default 0 = no limit) caps each change.
• Manual override – moving a brightness slider or pressing a preset switches automation off (turn it back on with the switch or Measure). The curve offset slider keeps automation on and applies at once.

🛠 Build from source

git clone https://github.com/AndriyOrlov/AmbientLightCalibrate
cd AmbientLightCalibrate/src
dotnet publish -c Release -r win-x64 --self-contained true -p:PublishSingleFile=true -p:EnableCompressionInSingleFile=true -o ../publish

Requires the .NET 10 SDK. Every tag v* is built by GitHub Actions and attached to a release.

🙏 Credits and attribution

AmbientLightCalibrate is created by Andrii Orlov (DeadSue) — github.com/AndriyOrlov · deadsue.art.

You are welcome to use, fork, modify and ship it, commercially or not, under the Apache License 2.0. The one thing asked in return is credit: keep the NOTICE file and mention "Based on AmbientLightCalibrate by Andrii Orlov (DeadSue)" in your project, app "About" box or documentation. A CITATION.cff is included for academic and tooling use.

Room light and screen luminance are measured with ArgyllCMS by Graeme W. Gill (AGPL-3.0), which AmbientLightCalibrate calls as external tools; it is not bundled in this repository.

🤖 Use by AI and LLMs

This repository may be read, indexed, used to train or fine-tune AI models, and used as context for AI-generated code. Code produced from it is a derivative work under Apache-2.0, so the same attribution applies: keep the copyright notice and credit "Andrii Orlov (DeadSue)". A short machine-readable summary is in llms.txt.

❤️ Support

If AmbientLightCalibrate is useful to you, you can support its development:

Monobank jar: send.monobank.ua/jar/7AVDtzYypi Jar card number: 4874 1000 3425 0244 A ⭐ on GitHub and a mention in your videos or posts help just as much. Thank you!

📄 License

Apache License 2.0 — see LICENSE and NOTICE. Copyright 2026 Andrii Orlov (DeadSue).

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🇺🇦 Українською

AmbientLightCalibrate — маленька програма в треї Windows, що сама підлаштовує яскравість моніторів під освітлення кімнати. Колориметр (i1Display / ColorMunki) із закритим розсіювачем раз на кілька хвилин міряє кімнату в люксах, а AmbientLightCalibrate через DDC/CI ставить кожному монітору потрібну яскравість у нітах. Змінюється лише підсвітка, тож калібрування (точка білого, гамма, LUT) лишається недоторканим. Монітори в режимі HDR програма не чіпає, а під час калібрування в DisplayCAL / ArgyllCMS / Calibrite стає на паузу.

Як почати: запустіть AmbientLightCalibrate.exe → ⚙ Налаштування → «Калібрувати» для кожного монітора (датчик на екрані, розсіювач відкритий, ~1 хв) → покладіть датчик біля монітора з закритим розсіювачем → увімкніть «Автояскравість». Інтерфейс автоматично українською, якщо Windows українська. Програма також нагадує про перекалібрування раз на 1 / 2 / 3 місяці: дату вона бере з активного SDR- і HDR-профілю кожного монітора.

Код відкритий під ліцензією Apache-2.0: користуйтесь, змінюйте, вбудовуйте, але зберігайте файл NOTICE і вказуйте автора — Andrii Orlov (DeadSue).

Підтримати розробку: Банка Monobank · картка Банки 4874 1000 3425 0244. Дякую!