Turn your device into an accurate light meter — for plants (PAR/PPFD/DLI) & more
4.62·10,629 reviews·500,000+ downloads
Photone - Grow Light Meter from Lightray Innovation provides research-grade plant light measurements (PAR/PPFD/DLI) using your phone’s camera, paired with heatmaps and time-series logging for indoor growers. With a 4.65 rating from 10,511 reviews and 500,000+ total downloads, Photone offers an ad-free, device-calibrated tool suitable for serious plant care. Not ranked in any top lists, it remains a focused solution for precise light measurement with optional upgrades to unlock more features.
Pros & Cons
High, device-calibrated accuracy using ISO/CIE standards
Ad-free user experience with minimal permission requests
Per-device calibration for immediate reliable readings
Heatmaps and exportable logs for deep analysis
Advanced features require in-app purchases to unlock
Diffuser is required for optimal accuracy; diffuser accessory available separately
About Photone - Grow Light Meter
Photone - Grow Light Meter is a tools app developed by Lightray Innovation GmbH.
How many times has Photone - Grow Light Meter been downloaded?
Photone - Grow Light Meter has been downloaded 570 thousand times. In the last 30 days, the app was downloaded 11 thousand times.
What is the rating of Photone - Grow Light Meter?
Photone - Grow Light Meter is rated 4.62 out of 5 stars, based on 11 thousand ratings.
Is Photone - Grow Light Meter free?
Photone - Grow Light Meter is free to download. The APK download size is 87.23 MB. The latest version available is 1.5.2. The last update was on August 14, 2026.
What are the requirements for Photone - Grow Light Meter?
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: Log all day: the Toolbox battery saver now ensures auto-logging runs use far less battery.
Get a detailed PDF report for Photone - Grow Light Meter with download trends, rating history,
and key performance statistics — useful for competitive research or tracking your own app.
Learn more
Are you the developer of this app? Join us for free to see more information about your app and learn how we can help you promote and earn money with your app.
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.
★★★★★Heather Marie McKeon· Mar 3, 2026
I don't EVER leave reviews. EVER. But when something is done right and done extremely well, I have to show my appreciation. I'll keep it short and sweet: YOU are here looking for what this app does. So was I. THIS APP DOES EXACTLY WHAT IT STATES IT WILL. I wanted an app that was free and could tell me the PAR of my grow light. It did that and just kept on giving. E. G *the helpful info section is so informative. It's a great read! No sign up, no pay info, no repeat ad pop-ups. This app ROCKS!
★★★★★France De Leon· May 16, 2026
This is such a game changer for growing plants indoors even outdoors you can check if the plant does really eat well
★☆☆☆☆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.
★☆☆☆☆Omar Robles· Aug 6, 2026
It only lets you check natural light and incandescent bulbs when 99 percent of homes have LED lights. This app sucks.
★☆☆☆☆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.
Google Play Rankings for Photone - Grow Light Meter
This app is not ranked
Technologies used by Photone - Grow Light Meter
12 permissions·20 libraries
Subscribe to see full permission and library details
Trust & Safety: Camera-based measurements rely on CAMERA permission, with Internet and network state access for syncing data. The app does not require location or Bluetooth permissions. It is advertised as ad-free and offers purchases (Lifetime unlock or Pro subscription) to unlock premium features. Google Play Billing handles purchases, and the app includes a diffuser accessory option for improved accuracy. Overall, privacy-conscious design with transparent upgrade paths and clear safety notes.
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.
