The app can be downloaded and tested for free. You'll find our test methods including all the results further down below. But you don't need to take our word for granted and can try it yourself. Since we're the creators of Photone our result could be potentially biased. It seems that Photone is the only plant light meter app on the App Store that is measuring accurately – we are blown away by the unsuitability of all the other plant lighting apps. TL DR: Our Recommendation Best Light Meter App For Plants: Photone Grow Light Meter If you don’t know why PAR is important or want to learn more, we recommend our article that covers the topic in detail.

A plant light meter must measure photosynthetically active radiation (PAR) as PPFD in the unit of µmol/m²/s. PAR MeasurementĪ light meter that only measures illuminance (lux or foot-candle) isn’t suited for plants as plants “see” light differently. The readings should be more or less equal under equal illumination. You can test this yourself by using the same app on different devices. Since there are so many different smartphones out there, this is a major challenge for developers of such apps. For a light meter app, this means that you should measure similar results, no matter which device you’re using.

In order for a light meter to be reliable and trustworthy, it must achieve similar results among different devices. The light meter’s measurement should now be four times as much due to the inverse square law. Then move your meter closer to the light by cutting the distance in half. You can easily test this yourself by taking a measurement at any distance from a light source. If a meter doesn’t measure linearly, it cannot be calibrated as the reading will always be off by a different amount. This means if the light intensity doubles, the reading should be twice as much too. The meter’s reading must be proportional (i.e. If you want to dig deeper into light meter accuracy, consider the ISO/CIE 19476 standard. Measuring light accurately is very hard to achieve, so a meter with an error of ☒0% can be considered as accurate enough for most applications. Obviously, a measurement device should provide accurate measurements. These are the four most important aspects of a plant light meter app: Accuracy If you’re looking for a light meter for applications other than plant lighting such as photography, health, or architecture, check out the Light Meter LM-3000 for exactly that.

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