Photone - Grow Light Meter

Turn your phone or tablet into a PAR meter. Measure PPFD, DLI, lux, foot-candles, and color temperature (kelvin) to give your plants exactly the light they need. Trusted by millions of growers, Photone is the only accurate plant light meter app.

How much light do your plants really get? Are your lamps hung too high, dimmed too low, or on for too long? Whether you grow houseplants or use a grow tent, greenhouse, hydroponics system, or aquarium, Photone answers these questions and more.

Photone is more than just a PAR meter: it gives you the tools and guidance to understand the numbers.

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
⎷ Correlated color temperature (CCT) in kelvin
⎷ Extended PAR (ePAR) including far-red light (ePPFD, eDLI) *

FEATURES

⎷ Industry-leading accuracy
⎷ Heatmaps — Create PAR, PPFD, DLI, and lux maps and export them as images
⎷ Logging — Track measurements over time as an interactive chart, Auto-Log sessions, and export or import them
⎷ Projected DLI — Get the daily light your plants receive instantly by entering how long your lamps are on ← perfect for grow lights
⎷ Actual DLI — Leave your device in place and use Auto-Log to sum up the light throughout the day ← perfect for sunlight
⎷ In-app guides
⎷ Light calculators and recommendations
⎷ Excellent low light sensitivity to detect light pollution for plants
⎷ Custom calibration option to align readings to another meter
⎷ No Bluetooth and location permission required
⎷ No ads
⎷ All grow light sources supported (Natural sunlight, LEDs, HPS, MH, etc.) *
⎷ Average and peak readings *
⎷ Hands-free "read aloud" function *
⎷ Special underwater measurement mode *
⎷ Pro support by real human experts *

* These features require an in-app purchase to fully unlock

HOW ACCURATE IS PHOTONE?

Photone matches the accuracy of professional handheld PAR quantum sensors costing hundreds of dollars. Here's how:

⎷ RAW sensor data — capture true light intensity using the camera, the most precise sensor in your device **
⎷ Pre-calibrated per device model **
⎷ Developed according to the ISO/CIE 19476 standard for light measurement
⎷ Continuously tested — we regularly calibrate and test on new devices

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. Details: https://lightray.io/diffuser/

** ENHANCED LIGHT MEASUREMENTS WITH THE CAMERA
Accurate camera measurements require a default calibration, available only for popular devices. Supported devices: https://lightray.io/diffuser/compatibility/

On other devices, Photone falls back to the built-in ambient light sensor (ALS). It works without a diffuser, but is far less accurate and reliable than the camera. Learn more: 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, it 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 7+ 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.

Terms and Conditions: https://growlightmeter.com/terms/
Privacy Policy: https://growlightmeter.com/privacy/

Recent changes:
This update ships minor fixes and improvements