My phone app vs lux meter results:
So I download the Lux Meter by My Mobile Tool. Out of the box there is a significant difference. Sitting on the desktop, the app reads 272 lux. My light meter shows 88.3. That's a 300% difference.
So I calibrate the phone app to get it as close to the lux meter as possible, within 4 lux or 4% margin of error.
I move the phone and lux meter just 2 foot on the desktop and compare readings again.
Just 2 foot away and now I have a 300% difference between to two measuring devices again. OK, that's low light. How about in the tent? I checked inside at each plant top. My front plants are 17,000 on the lux meter and 20,000 on the back plants. The 3,000 difference is most likely due to having the front door of the tent open and not getting any reflective light from the tent side. The phone app came in at 27,000 across the board. Thats a 35-58% difference. So in low light situations, the phone app reported way less light, and in high light situations, it over reported. I tested it with another app and got similar results. Different phone maybe? My new Coolpad Legacy vs my year and a half older ZTE Blade Max Pro, still about the same. For full disclosure though, the ZTE and Coolpad have basically the same specs. Conclusion...I had no consistency in my results. One moment its under reported, the next its over reported, the numbers on the screen are really meaningless. No stars - would not recommend.