Light is such an important factor for plant growth and wondering about your plants’ lighting can certainly keep you up at night. Luckily enough there is a simple solution that does not cost an arm and a leg: A light meter app.
I tested all relevant plant light meter — or PAR/PPFD meter to be precise— apps on the Google Play Store so you don’t have to. This article provides an overview and recommendations about them. So read along to find the Android plant light meter app that is right for you!
Are You an iOS User?
If you’re looking for an iOS app, check out my other article entirely focused on iPhone and iPad.
The Dangers of Android Light Meter Apps
There are light meter apps for Android — in fact, many of them. The issue with all the Android light meter apps that I am aware of is the way they measure: All of them seem to use the built-in ambient light sensor that can easily be accessed by any software developer. This seems great at first glance, as the ambient light sensor is directly delivering you the illuminance in lux that you can then use in your app. However, using the ambient light sensor incorporates some issues:
- It can be dangerously inaccurate. The sensor is mainly used to dim the screen brightness according to the available ambient light, which does not require much accuracy at all.
- It is measuring illuminance. Illuminance represents light as perceived by the human eye. For plants, we need to measure PPFD that resembles the PAR spectrum.
- It is highly directional. High-quality light meters respond to light from different directions based on the cosine-law, which the ambient light sensor does not. This means that depending on the reflectivity of your surrounding area (e.g. grow room), you’ll get different measurements.
When diving deeper into the usage of the ambient light sensor, it also becomes evident that its accuracy, precision, and directionality is highly dependent on the phone model that you are using. Some seem to measure acceptably accurate within a given range whereas others are just dangerous to use for anything else but changing the screen brightness. This also leads to the issue that Android light meters might seem trustworthy due to acceptable results on a certain phone model in a certain scenario.
Mitigating those issues requires skill and high expertise in light measurement. Therefore, not all light meter apps are of equal quality.
Android PPFD Meter App Test
When comparing light meter apps, we’ll look at the following factors:
- Ease of use
- Measurement of PAR as PPFD
- Accuracy and precision
- Developer activity (supporting the latest devices, offering support, etc.)
I’ll cover each of these criteria in my subsequent test and recommendation to gain you the peace of mind needed when it comes to choosing your PPFD meter app for Android.
As we are first and foremost comparing light meters, they need to measure accurately. My tests revealed that most apps are comparingly accurate when it comes to “white” full spectrum lighting, but heavily differ when measuring “blurple” red / blue LED light. The accuracy of all illuminance-based plant light meter apps comes down to the built-in ambient light sensor that proves fairly accurate on our Samsung Galaxy S10 test device. When converting this illuminance measurement to PAR however, the apps differ wildly!
A small error is to be expected as no light meter exactly measures the same, but any error exceeding 10% becomes noteworthy whereas errors upwards of 30% even become dangerously critical in some scenarios.
You can find more information on the test setup and methodology at the end of this article.
Recommended for Everyone: Photone — Grow Light Meter for Plants
The Photone — Grow Light Meter for Plants is a very well made and professional looking app by an established developer. The Android version is still labeled as a Beta (in April 2022) and not necessarily as accurate as their iOS version, but also no less accurate than the other apps I’ve tested. Especially the red/blue LED measurement was the most accurate of all and the whole app can be calibrated to exactly match any reference. The app also includes helpful guides and a calculator for cannabis, houseplants, and fruits or vegetables to assist us with our grow lighting decisions, providing a further edge over using the other apps.
Recommended for Technicians: Tent Buddy
Tent Buddy is a fairly simple app for anyone that already understands the technical details of PAR, PPFD, and DLI and seems to be tailored to cannabis. The app is still in its version 1.0.0 since years and there is no developer activity so this can be an issue on the latest devices and Android versions. For most advanced growers, it includes what is needed and does a good job delivering it. However, it does not allow for any calibration so you might have to do some manual calculations as well. Never use it to measure the PPFD of your red / blue LED equipped grow room as the error in my test was enormous!
Not Recommended: PPFD Meter — Grow Light Meter
The PPFD Meter app includes many features for the advanced indoor horticulturist and is regularly updated. This is great if, for instance, you want to create your own PAR map and know exactly what you do, but also increases the app’s complexity which makes it a bit hard to configure. Still, the app offers all the features you need and can aid your grow lighting decisions. If you don’t need all of those features, it can be viewed as a more complicated version of Tent Buddy (including exactly the same light settings) that also bombards you with advertising or wants to sell you on a subscription. Also, never use it to measure the PPFD of your red / blue LED equipped grow room as the error was enormous!
I also tested the PPFD Meter app with a Uni-T UT383 BT lux meter that can easily be integrated via Bluetooth and promises increased accuracy. However, this has not been the case in my tests: The Uni-T UT383 BT meter measured way higher than my $800 HIOKI FT3425 reference lux meter and was especially worse at measuring red / blue LED lighting with an error of 221%! Using the Bluetooth meter didn’t increase accuracy on my device but still offers some usability benefits that might come handy.
Not Recommended: Lux to PPFD Sensor
The Lux to PPFD Sensor app is very similar to the Tent Buddy app but supports less light sources. For instance, none of my LED lights was covered on the selection and I was forced to use the sunlight setting as the closest match. The app is still in its version 1.0.0 since years and there is no developer activity so this can be an issue on the latest devices and Android versions. I don’t recommend to use it at all.
I wanted to perform a test that is both accurate and representative for the usage in growing plants. I therefore used two of the most common grow lights: A full spectrum LED Quantum Board, that is used by many home- and professional growers alike, and a “blurple” Phlizon Red / Blue LED. I put each lamp fixture into a light proof grow box and varied the height to achieve different light intensity levels.
To provide the PAR reference measurements, a NIST traceable Apogee SQ-520 Full-Spectrum Smart Quantum Sensor (costing around $500) was used.
All Android apps were tested on a Samsung Galaxy S10 running Android 10 and also with the most recent app version available from Google Play as of April 2022.
For me, this article has been an interesting test: Many apps claiming to do the same, yet they are completely different. I hope that this article is comprehensible and makes sense. If you have any inputs, please let me know! If you think that my measurements are flawed: Please challenge me! Recreate a stable test setup and measure those apps against an accurate and reliable reference. I’m very curious and would be pleased to see your results as well.
The measurements above provide me with absolute confidence that the Photone Grow Light Meter is an excellent alternative to any hardware PAR meter — especially at a $500 price difference!