Turn your device into an accurate light meter — for plants (PAR/PPFD/DLI) & more
4.65·10,473 reviews·500,000+ downloads
Photone turns your Android device into a precise plant light meter, measuring PAR, PPFD, DLI, lux, and color temperature with camera-based sensing. Free to start and ad-free for basic use, it offers device-specific calibration, guides, and grow-light tools. With 500,000+ total downloads and 12K in the last 30 days, Photone has established a strong foothold in the TOOLS category.
Pros & Cons
Ad-free basic experience and no unnecessary permissions.
Device-calibrated readings for reliable results across devices.
Free to download with paid upgrades (Lifetime unlocks and Pro subscription)
Recent 30-day downloads are zero, indicating no new downloads in the last month.
Some advanced features require in-app purchases to unlock.
DIFFUSER REQUIRED for accurate measurements; diffuser can be DIY or a dedicated accessory, which may add setup steps.
About Photone - Grow Light Meter
Photone - Grow Light Meter is a tools app developed by Lightray Innovation GmbH.
Download Statistics
Photone - Grow Light Meter has been downloaded 560 thousand times. In the last 30 days, the app was downloaded 12 thousand times. It is ranked in the top 100 tools apps.
User Ratings
Photone - Grow Light Meter is rated 4.65 out of 5 stars. The rating is based on 10 thousand ratings.
App Information
Photone - Grow Light Meter is FREE to download. The APK download size is 88.35 MB. The latest version available is 1.5.0. The last update was on July 11, 2026.
Technical Requirements
The app has a content rating of Everyone. The app has been available on Google Play July 2021.
Description
Take the guesswork out of plant lighting with Photone, the most accurate plant light meter app. Measure PAR, PPFD, DLI, lux, foot-candles, and color temperature (kelvin) directly with your phone or tablet.
To measure light with research-grade accuracy, Photone uses the most precise sensor in your device: the camera**. It rivals professional handheld PAR meters, and goes even further by helping you interpret the numbers with in-app guides, tools, and additional features.
MEASUREMENTS
⎷ Photosynthetically Active Radiation (PAR) as PPFD in µmol/m²/s ⎷ Daily Light Integral (DLI) in mol/m²/d ⎷ Illuminance in lux or foot-candles ⎷ Light color temperature in kelvin ⎷ Extended PAR (ePAR) including far-red light (ePPFD, eDLI) *
TOOLBOX
⎷ Heatmaps — Create exportable PAR maps, PPFD maps, DLI maps, lux maps, and more ⎷ Logging — Track measurements over time as an interactive chart, Auto-Log sessions, and export them
FEATURES
⎷ Industry-leading accuracy ⎷ Pre-calibrated for your device model ** ⎷ Excellent low light sensitivity to detect light pollution for plants ⎷ No ads ⎷ No Bluetooth and location permission required ⎷ In-app guides ⎷ Light source selection for every type of grow light (LED, HPS, CMH, etc.) * ⎷ Average and peak readings * ⎷ Plant light calculator ⎷ Hands-free “read aloud” function * ⎷ Special underwater measurement mode * ⎷ Custom calibration option ⎷ Premium support for advanced grow questions *
* These features require an in-app purchase to fully unlock
DIFFUSER REQUIRED
Like every real light meter, Photone requires a diffuser to measure accurately**. A diffuser scatters incoming light evenly on the sensor and prevents hotspots. While it may sound complex, the solution is surprisingly easy. You have two options:
1) Easily build a diffuser yourself in less than a minute using standard printer paper. This is accurate enough for most use cases.
2) Get the dedicated Diffuser Accessory (free worldwide shipping) for best accuracy and convenience. More details on https://lightray.io/diffuser/.
** ENHANCED LIGHT MEASUREMENTS WITH THE CAMERA Accurate light measurements with the camera require a default calibration, which is made available only for selected higher-quality devices. Check the full list of supported devices here: https://lightray.io/diffuser/compatibility/
On devices without default calibration, Photone automatically falls back to the built-in ambient light sensor (ALS). While the ALS works without an external diffuser, it is far less accurate than camera-based measurements. Learn more here: https://growlightmeter.com/guides/different-light-intensity-sensors/
UPGRADE OPTIONS
Photone is free to download and use, with no ads or hidden costs. To unleash its full potential, Photone offers two types of upgrades: → Lifetime unlocks — one-time purchase, always restorable via your Google Account → Pro subscription — full access for as long as you subscribe, cancel anytime
Photone took 5+ years of R&D to develop. Upgrading unlocks powerful features and keeps the app ad-free for everyone. As a member of 1% for the Planet, we donate at least 1% of all revenue to environmental non-profits — so every purchase helps both your plants and the planet.
ACCURACY
Apps developed by Lightray Innovation are developed according to the ISO/CIE 19476 standard. Thanks to RAW image processing and a default calibration per device model they’re able to match the performance of high quality traditional hardware light meters. To ensure quality we rigorously test our apps regularly on upcoming devices.
DOWNLOAD FOR FREE. TRUSTED BY MILLIONS.
Optimized for plant growers and indoor gardeners – whether you’re growing in a grow tent, greenhouse, hydroponics system, an aquarium, or just want the best quantum meter app for your LED grow lights, Photone has got you covered.
Terms and Conditions: https://growlightmeter.com/terms/ Privacy Policy: https://growlightmeter.com/privacy/
Recent changes: Measure your real Daily Light Integral (DLI): the Toolbox logging tool now supports day-long auto-logging and calculates the DLI from all measurements.
Get a detailed PDF report for Photone - Grow Light Meter with download trends, rating history,
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Comments on Photone - Grow Light Meter for Android
★★★★★Jeremy Haynes· Dec 2, 2025
Tested against an actual meter. Compared to other apps, this is hands down the most accurate to do PPFD measurements. At most depending on one the settings you have there could be roughly 5% difference. So that said, if you can not get the Diffuser accessory or get your hands on Diffuser Paper (matte on one side and glossy on the other) then you will most likely be reading slightly out. Calibrate the app to your phone and set to your type of light for the Best Reading.
★★★★★Mr. Rosa· Dec 26, 2025
Great app for reading and setting up perfect growing conditions for all types of plants. Definitely use this app on the daily for my growth space & would recommend to all 💯
★★★★★Brad Hepler· Feb 19, 2026
This app has helped immensely getting the light right for indoor vegetables. Having the ability to adjust hours of exposure to get DLI at various heights helps to switch between various needs (peppers vs lettuce)
★☆☆☆☆Elaine Thompson· Jun 24, 2026
The app says it's not calibrated for my S26 and may be inaccurate. The solution: calibrate with a photometer I trust. If I had a photometer I trusted, why would I be using my phone? It also falsely detects a diffuser, even though the app says not to use one. I'm hoping they get the S26 resolved but until then I'm uninstalling. It's impossible to know what I'm actually measuring.
★☆☆☆☆Silent Camper· Jul 14, 2026
All features now require payment, I've had this app since the start and even got a new phone to use it on. Now they paywall all the LED features like they did on IPhone. At this point may as well use an old phone and sideload and older version. Edit to reply to photon: Pay for something that was already free before? Hell no, I would rather go buy a real PPD meter at that point. I used to recommend many people get this app but not something I will do anymore. it's always a bait n switch.
★☆☆☆☆Jax Koyote· Apr 27, 2026
Booooooooo! Why are you charging so much per yr just to use it to get proper readings, and we have to buy a diffuser. no, thank you.
Google Play Rankings for Photone - Grow Light Meter
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Photone - Grow Light Meter is requesting 12 permissions and is using 20 libraries.
Show details
Trust & Safety: Permissions include CAMERA, INTERNET, ACCESS_NETWORK_STATE, VIBRATE, WAKE_LOCK, BILLING, CHECK_LICENSE, BIND_GET_INSTALL_REFERRER_SERVICE, and AD_ID. The app is described as ad-free for basic use and offers premium upgrades; no location permission is requested. It emphasizes device calibration and ISO/CIE 19476-based accuracy, with standards-compliant RAW image processing and regular testing across devices.
Each subscription will automatically renew 3 days before the expiration date for
the same time period. Subscriptions can be cancelled at any time before the renewal.
