# Photone - Grow Light Meter — Perfectly light your plants!

> Accurate plant light meter app measuring PAR, PPFD, DLI, lux, and kelvin. (iPhone/iPad app by Lightray Innovation GmbH.)

- Source: https://appshunter.io/ios/app/photone-grow-light-meter/id1450079523 (this page in markdown: same URL + `.md`)
- Developer: [Lightray Innovation GmbH](https://appshunter.io/developer/1031383431)
- Category: Utilities
- Price: Free with in-app purchases
- Rating: 4.60/5 from 4,889 App Store ratings · 230 written reviews indexed
- Age rating: 4+
- Requires: iOS 15.0 · 80 MB
- Languages: German (Germany), American English, French (France), Japanese, European Portuguese, Russian, European Spanish, Chinese (Traditional, Taiwan), Chinese (Simplified, China)
- Released: 2019-04-24
- Data updated: 2026-08-27
- Monetization: free with in-app purchases
- User reviews in markdown: https://appshunter.io/ios/app/photone-grow-light-meter/id1450079523/reviews.md

## What is Photone?

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. Its unique measurement algorithm works directly with the RAW camera sensor data to capture true light intensity. 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, comparable to professional PAR quantum sensors
⎷ Pre-calibrated for your specific device
⎷ 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 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/.

(!) Do not rely on apps that do not require a diffuser. They are inaccurate because they ignore the basic physics of light measurement.

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 Apple 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/

## Key features

- Measure PAR, PPFD, DLI, lux, foot-candles, and kelvin
- Research-grade accuracy using device camera
- Pre-calibrated for specific devices
- In-app guides and tools
- Light source selection for various grow lights
- Hands-free 'read aloud' function

## Pricing and in-app purchases

Base price: Free.

**Subscriptions**

| Subscription | Price | Period |
| --- | --- | --- |
| Photone Pro (Monthly) | $5.49 | per month |
| Photone Pro (Yearly) | $29.49 | per year |

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| MH lifetime unlock | $5.49 | one-time |
| LED Full Spec. lifetime unlock | $6.49 | one-time |
| HPS (Standard) lifetime unlock | $5.49 | one-time |
| HPS DE lifetime unlock | $5.49 | one-time |
| Photone Pro Lifetime Unlock | $97.00 | one-time |
| LED (Red / Blue) Lifetime Unlock | $6.49 | one-time |
| FL (Daylight) Lifetime Unlock | $5.49 | one-time |
| Sun Lifetime Unlock | $5.49 | one-time |
| LED (Blue / White) Lifetime Unlock | $6.49 | one-time |
| LED (Full Spectrum) Lifetime Unlock | $6.49 | one-time |
| LED (Full Spectrum + Red) Lifetime | $6.49 | one-time |


## What do users think of Photone?

Overall sentiment: neutral

**Pros**

- 🚀 Accurate readings
- 💡 Helpful for growing plants
- 👍 Easy to use
- 🚀 Saves money compared to expensive meters
- 👍 Useful for adjusting lighting

**Cons**

- 🐛 Inconsistent readings
- 💰 Expensive in-app purchases
- 🔒 Requires additional equipment (diffuser) to work properly
- 🐛 Readings not accurate without calibration
- 🔒 Limited functionality in free version

**Commonly reported bugs**

- Readings don't change with proximity
- Diffuser requirement not made clear upfront
- Purchased features not working as expected

**Most requested features**

- Add calibration feature
- Expand supported light types in free version
- Improve accuracy across different devices
- Provide a one-time purchase option instead of subscription

## Recent user reviews (10 of 230)

All indexed reviews: https://appshunter.io/ios/app/photone-grow-light-meter/id1450079523/reviews.md

### 5/5 — Angela Rocks!

*2026-08-14, version 4.5.1*

I haven’t tried the diffuser yet, I’m still in process of “growing my orchid set up”. However the customer service to include the links needed for learning and buying what I need were all given by Angela through email correspondence.
It’s been so long since I had actual customer service -I forgot how nice it feels!
I wish the same team would be involved in all aspects of my life!!!
You all are awesome!

### 2/5 — No support

*2026-08-14, version 4.5.1*

I paid for the diffuser. I paid for the led with red light reader. It worked for a while. Now I get no reading at all. Removed and reloaded with no improvement. Go to support page. No support at all. Zero. Dead end on app. Wants you to buy “pro” for support. I just want readings. All my settings are good. Still won’t give any readings at all

### 3/5 — Expensive!

*2026-07-21, version 4.5.0*

This app works but I am not paying $100 for full functionality and I like to own things completely. This monthly subscription thing is nonsense. I would pay $30 to own this app with all its functionality. Thats what it’s worth and you would make more sales and have happier customers if you were not so greedy. BTW you can just use Rizla paper as a filter. Saves flaff with scissors and tape!

### 2/5 — Can’t test sunlight for free

*2026-07-15, version 4.5.0*

I made their paper diffuser and started measuring an area only to be stopped. If you want to measure sunlight, you have to pay over $5.

### 1/5 — Nothing free about this

*2026-06-09, version 4.4.0*

Whichever light you want to measure it costs , stop touting this app as free. Unless you count the free download .

### 5/5 — You will not find better

*2026-05-21, version 4.3.3*

100% perfect no quibble

### 5/5 — Amazing app for lighting ideas

*2026-05-18, version 4.3.2*

Been using this for about a week or two it’s a pretty good app works as it should however, sometimes it’s hard to hold the paper under the screen or camera and looking at the screen under the bright light. It’s hard to see the exact numbers, but I figured it out. Hopefully, it’s been fixed in the latest update props to this dev team.

### 1/5 — “Free” is misleading

*2026-05-16, version 4.3.1*

Wanted an app to measure indoor natural light & this one rated really well. Downloaded it & discovered “sun” aka natural light is locked unless you purchase a subscription/membership. This light source is likely the most commonly used for growing plants but yet needs a subscription? No thanks.

### 1/5 — Teste

*2026-05-09*

Poderia dar alguns dias de teste gratuitos antes de comprar.

**Developer response:** Olá PoA,

Obrigada pelo teu feedback. Podes testar as funcionalidades da aplicação gratuitamente com uma das fontes de luz gratuitas durante o tempo que quiseres. Isso deve dar-te uma boa ideia se vale a pena ou não pagar os cerca de 5 $ únicos. É uma pena que, por causa disso, nos dês apenas 1-🌟 😢

Cumprimentos,
Angela e a equipa Photone

### 1/5 — don’t bother

*2026-04-18, version 4.3.1*

measuring led lights is paywalled

## Frequently asked questions about Photone

### What does Photone do?

Photone is a mobile application that functions as a highly accurate light meter for plants. It uses your device's camera to measure various light metrics such as PAR, PPFD, DLI, lux, foot-candles, and color temperature (kelvin). This data helps users understand and optimize the lighting conditions for their plants.

### What are the key features of Photone?

Key features include industry-leading accuracy comparable to professional PAR sensors, pre-calibration for your specific device, and excellent low light sensitivity. It also offers in-app guides, light source selection for different grow lights, and a hands-free 'read aloud' function. Some advanced features like Extended PAR and underwater measurement modes require an in-app purchase.

### How much does Photone cost?

Photone is free to download and use with all basic features, and it contains no ads. To unlock its full potential and access advanced features, users can opt for a one-time lifetime unlock purchase or a Pro subscription. These upgrades support the app's development and environmental initiatives.

### What devices is Photone compatible with?

The app description implies compatibility with smartphones and tablets that have a camera. While specific operating system versions are not mentioned, it is generally designed to work on modern mobile devices. The accuracy of measurements can be influenced by the quality of the device's camera sensor.

### What are common use cases for Photone?

Common use cases include optimizing grow light setups for indoor plants, ensuring plants receive the correct amount of light for photosynthesis, diagnosing lighting issues, and fine-tuning lighting for specific plant species. It's also useful for hobbyists and professional growers alike to achieve better plant growth and health.

## Version history (last 5 releases)

### 4.5.2 — 2026-08-19

Log all day: the Toolbox battery saver now ensures auto-logging runs use far less battery.

### 4.5.1 — 2026-08-06

This update adds a helpful info section to Logging exports in Excel and reduces CPU load during measurements.

### 4.5.0 — 2026-07-15

Measure your real Daily Light Integral (DLI): the Toolbox logging tool now supports day-long auto-logging and calculates the DLI from all measurements.

### 4.4.0 — 2026-06-08

Added the Photone toolbox — featuring two powerful tools:
- Heatmaps: Easily create and share beautiful PAR and ePAR maps.
- Logging: Record your PPFD, DLI, and lux measurements over time and export them as Excel spreadsheets.

### 4.3.3 — 2026-05-21

The light calculators in the in-app guides have been completely reworked. Easily convert between units, get recommendations, calculate exactly how much light your plants need, and grow with confidence.

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## More apps by Lightray Innovation GmbH

- [Light Meter LM-3000](https://appshunter.io/ios/app/light-meter-lm-3000/id1554264761)

All apps by Lightray Innovation GmbH: https://appshunter.io/developer/1031383431

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-27.*