Lux Light Meter

I’m using an app on my Galaxy S9+ called “Lux”. At the top of my plants it read about 26,000. That calculates to 598 umol/sm2. How accurate do you more experienced growers think this “technique” is? And is this an acceptable amount of light for the veg. stage?

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Yes, ~600 PPFD is a really good number for veg stage. The “standard” for flowering is 800 PPFD or better.

The “technique” is valid if the conversion is done correctly for your specific light.


Thanks a lot! I’ve been checking on them every 10-15 min. to make sure they’re not cooking. LOL. Slowly but surely things are starting to come together and making some sense. The light I’m using is a SonoFarm Pro-4000 in 5’x5’.

Is the conversion table (lux to PPFD) you are using specific to the Sonofarm Pro-4000?

No. I just converted the lux I got on my phone. It’s just slightly lower on the fringes. I suppose I could take several measurements and get an average?

location and distance of the “meter” to the light makes a big difference. I have a Pro-4000 too. I am sure you have seen its PPFD maps

Is your dimmer accurate? Mine is off quite a bit based on Kill-a-watt meter readings.

How did you test your dimmer?

I’ve just got mine turned up half way.

I used a Kill-a-watt meter

When I first set up the light I wanted around 300 watts. This would be slightly higher than the lights it was replacing. I set the dimmer at 80%. It didn’t look right so checked the watts drawn with the meter. 80% was only drawing 200 watts.
I just recently informed Sono Farm of the faulty calibration and Reuben is supposed to get back to me this week. They seemed receptive to correcting the defect but I will have to see what they propose.
The good news is at 100% it does in fact draw 400 watts. Other wise I am very happy with the light. The quality of its assembly and components is very high.