First and foremost: Photone is free to download and use. Its core features are free and will stay free, and you'll never see ads in our apps. That's our gift to the community.
What's Free
- Measure light with solid accuracy (better than any other app you'll find; pre-calibrated for over 250 unique devices)
- Light intensity readings — PAR (PPFD and DLI) and illuminance (lux and fc)
- Logging and charting
- Heatmaps to map the footprint of your grow
- Calibration option to adjust your device's readings to a reference
- In-app guides on plant lighting
- Support resources on our website
- Tons of helpful content on our blog
Why It Isn't Entirely Free
We're a small team, and we've spent over 8 years on Photone. We were the first to build a genuinely accurate camera-based light meter. Until we did, blogs and even scientific papers insisted it couldn't be done. Proving them wrong took relentless, expensive work, and keeping it that accurate still does: we develop the software, test it across a huge range of phones and tablets, calibrate every supported device individually, maintain a lab full of reference equipment, and research the plant-lighting know-how that our competitors then quietly copy. All of that has to be paid for somehow — and a small set of optional features carries that cost.
We're not trying to squeeze anyone. Quite the opposite: The more growers support Photone, the more sustainable Photone becomes, the better we can keep prices for everyone. Every upgrade you buy helps us get there. Read along to see what you can unlock.
Going Further
If you use Photone regularly, there are two ways to get more out of it.
Unlock Your Light Source
Selecting your exact light source compensates the spectral error and noticeably improves accuracy. It's a one-time purchase of just a few dollars (around $3–7, depending on the light source and your local taxes), and well worth it if you measure on a regular basis. Need more than one? Every light source setting is included in Photone Pro.
Photone Pro
Photone Pro is for serious growers, or anyone who just wants the best there is. It unlocks everything:
- Every light source setting
- ePAR readings (extended PAR range, 400–750 nm)
- Pro settings (advanced readings, spirit-level indicator, underwater mode, custom HOLD-button behavior, Read Aloud)
- Pro Guides (in-depth guides for cannabis, houseplant, and coral lighting)
- Pro Support (help with your specific issues — from actual humans!)
- Fully unlocked Toolbox (no heatmap watermark, unlimited logs, .xlsx export)
- Watch connectivity (iOS only)
How to Get It
Start with the monthly subscription at $5/month to see whether you actually need these features and cancel anytime. If it's good value for you, switch to the yearly plan and save 50%.
And because we don't love the “everything is a subscription” trend either, Pro is also available as a one-time purchase. The price tag is higher, but you get every feature the app will ever offer, with updates for life.
With most software, paying once freezes you in time. Let's take your old standalone GPS nav device that still might switch on, but its maps are years out of date, routing you down roads that no longer exist. Photone is the opposite: we keep updating it for new devices and adding features, so your purchase keeps getting better even years down the road.
FAQ
What About Cheaper Apps?
We'll be blunt: they're simply inaccurate! And an inaccurate meter is worse than no meter at all, because you never know when to trust it.
Measuring light properly isn't a matter of being off by a flat 20% you could just correct for. It involves linearity corrections, spectral error, calibration error, cosine correction and more — each of which shifts depending on where or what light you're measuring. Getting all of that right is exactly what we've spent years researching. (Because this topic is complex, we'll try to cover this in a dedicated article. Still working on it …)
Why Don't You Just Show Ads?
Ads would mean tracking you and collecting your data for targeting. Photone is private by design: no account, no records. Ads are also intrusive and distracting, and a measurement tool simply shouldn't have them.
Android Used to Be Free. Why Did You Change That?
Photone was free throughout the Android beta, up to version 0.6.6 in December 2024. With the 1.0.0 release in January 2025 we added Pro features.
Providing a light meter app on Android is genuinely expensive for us. There are countless devices, each with slightly different cameras, sensors, and OS behavior — and every one has to be calibrated individually. We were making heavy losses on Android; it cost far more to develop than it earned. To keep it sustainable, we had to align the payment model with iOS and with version 1.3.0 in April 2026 we made most light-source settings paid.
A note for our long-time users: if you used Photone during the beta, or before version 1.3.0, you keep every feature you already had — as long as you don't uninstall the app. Because there's no user account, a fresh install treats you as a new user, and since those features were never a purchase, there's nothing to restore. (Actual in-app purchases are tied to your Google account and can always be restored.)
Can I Transfer Purchases Between iOS and Android?
Unfortunately not. Apple and Google both prevent it. We don't like it either, and we're looking for a workable solution, but haven't found a good one yet.
Why Don't You Have a User Account?
An account would mean storing your data: who's using the app, and so on. We'd rather not, and we suspect you'd rather we didn't either.
How Much Are the Upgrades?
- Single light-source setting: ~$3–7 one-time
- Photone Pro: ~$2.50/month billed yearly, ~$5/month billed monthly, or ~$80 one-time (see what's included)
Prices vary because each country/state has different taxes. E.g. Hungary, Sweden and Denmark add over 25%, Germany almost 20%, etc. These change so frequent that we can't list exact figures here.
What About the Diffuser Accessory?
The Diffuser & Cosine Corrector accessory is an optional add-on that makes Photone easier and more reliable to use: simpler placement, better reproducibility, and best accuracy thanks to proper cosine correction. It's entirely optional, but worth it if you measure on a regular basis.
It's manufactured and assembled in Switzerland. Designing an optical accessory that fits almost any smartphone took years, plus investment a full manufacturing and assembly line. Between that and covering quality control, packaging and worldwide shipping, the price you pay is more of a cost-covering than a revenue driver for us.
Didn't find what you were looking for? We genuinely value your feedback. Let us know: