Photone - Grow Light Meter

In-app purchases
4,7
8,71K reviews
100K+
Downloads
Content rating
Everyone
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About this app

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.

Photone uses the most precise sensor in your device – the camera – to measure light with research-grade accuracy**. Photone rivals professional handheld PAR meters in accuracy, and goes 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) *

FEATURES

⎷ Industry-leading accuracy, comparable to professional PAR quantum sensors
⎷ Pre-calibrated for your specific device **
⎷ No ads
⎷ 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 to align readings to another meter
⎷ 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 about the differences between the two sensor types here: https://growlightmeter.com/guides/different-light-intensity-sensors/

UPGRADE OPTIONS

Photone is free to download and use with all basic features without any 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 more than 5 years of R&D to develop. Upgrading not only unlocks powerful features, but also supports future development and keeps the app ad-free for everyone. As a member of 1% for the Planet, we donate at least one percent of all revenue to environmental non-profits — so every purchase helps both your plants and the planet.

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 are just looking for 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/
Updated on
31 Jul 2025

Data safety

Safety starts with understanding how developers collect and share your data. Data privacy and security practices may vary based on your use, region and age. The developer provided this information and may update it over time.
No data shared with third parties
Learn more about how developers declare sharing
This app may collect these data types
App activity, App info and performance and Device or other IDs
Data is encrypted in transit
You can request that data be deleted

Ratings and reviews

4,7
8,6K reviews
Joey Farley
18 January 2025
This app has been fantastic, I have the diffuser accessory now, and it made it a lot more stable. I have been using paper and it was reading quite a bit lower than it actually was and I always thought I was having to run my plants with low light and I felt bad always trying to push them thinking I was running low. Now, with the accessory, it seems to be much better. I had to raise my lights and dim one of them, and after a couple of weeks, everything is great.
18 people found this review helpful
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Lightray Innovation GmbH
18 January 2025
Hi Joey, 🤩 Wow, thank you so much for this review and for taking the time to share your insights and experiences with our app and our diffuser and cosine corrector accessory with the community!🙏 It's really cool to hear that we contribute to the well-being of your plants and your satisfaction with light measuring ☺️ Kind regards, Angela & team
Samantha
14 April 2023
Great concept, quick response from support. I had an issue with a tip not dismissing and they got back to me the next day from the other side of the planet. The light readings are pretty far out from my actual meter, but hopefully they can fine tune it for better accuracy. Be sure to look through the extras on the site, they have a great little start of a plant database with light info for various species - looking forward to this being integrated fully into the app in time. Well done, devs!
37 people found this review helpful
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Lightray Innovation GmbH
15 April 2023
Hi Samantha, Thank you very much for your insightful review! We're happy to hear that you like our app :) If you have an actual meter and want both devices to read the same you can simply calibrate according to that. We have a guide showing how here: https://growlightmeter.com/guides/how-to-calibrate-photone/ Best, Dominik and the Photone Team
G B
04 August 2025
way off from an actual meter. this was showing 300-350. actual light meter showed 1000+. same distance.
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Lightray Innovation GmbH
05 August 2025
Hi GB, Unfortunately, your specific device doesn't yet support enhanced light measurements using the devices front camera. So the measurement depends on the built-in ambient light sensor (ALS) inside your device. Cheaper devices tend to have inaccurate sensors. However, given this huge difference, it might also be worthy to check your light meter.

What's new

This update features an improved automatic diffuser detection that works on all possible Android devices. Among that we’ve fixed a few minor issues.