Lux/ppfd/DLI chart for Autos?

[YoungGrassh0pper]

That's because smartphone sensor hardware fundamentally isn't set up properly for this use case. The light sensor on the phone doesn't have a translucent dome for cosine correction, so instead of measuring light coming from a range of angles, over a wider area, it's just measuring light hitting the tiny sensor straight on. It's like measuring brightness through a pinhole, when really what you want for growing is to measure how much light hits the leaf surface area. Putting white paper over the lens will definitely affect the readings, but it isn't likely to make them more accurate. They'll take your money either way, though.

You can get an actual lux meter for about $25. I find mine invaluable for finding spots in the canopy that are getting significantly more or less light than the rest, usually I can't tell just by looking.

What lux meter do you use, Parsings? I use the photon app they’re alluding to and I’ve seen positive results, but I would like to dial it in more if possible.

 

[parsing_trees]

I use a Dr.meter LX1010B, which was about $20, and has a sensor part I can move around into the far corners of the tent while the readout is still in front of me. I can't compare it to other meters at that price point, but it seems quite good enough for use by other geeky homegrowers.

My comment about the phone hardware being inappropriate for measuring light intensity in a grow comes from doing embedded development on a commercial product which used an ambient light sensor (for a non-horticultural use case). I can't get into the details.

 

[YoungGrassh0pper]

I use a Dr.meter LX1010B, which was about $20, and has a sensor part I can move around into the far corners of the tent while the readout is still in front of me. I can't compare it to other meters at that price point, but it seems quite good enough for use by other geeky homegrowers.

My comment about the phone hardware being inappropriate for measuring light intensity in a grow comes from doing embedded development on a commercial product which used an ambient light sensor (for a non-horticultural use case). I can't get into the details.

Thanks! I’ll look into it. Thanks for giving context on your reply, also.

 

[Skunkymonkey]

Also, there's an app for iphone called Corona that has a DLI and PPFD meter: https://growlightmeter.com/

This guy on youtube runs a comparison to a real Lux meter, so it seems the app is pretty solid and will get you close for just a couple bucks. Note that you have to put a piece of white paper over the camera lens when using or the numbers will be all out of whack. I think the app actually makes note of that little hack now, but didn't when I first got it.

If. You use that photone app with a Samsung or android device the numbers are completely off I had to use a ppfd chart and recalibrate my phone to reach the levels they are supposed to be

 

[Death The Cultivator]

If. You use that photone app with a Samsung or android device the numbers are completely off I had to use a ppfd chart and recalibrate my phone to reach the levels they are supposed to be

Every Android phone possess a different light sensor, not intended for photon measurement but lux in the blue and red spectrums. Works well for iphones because they all mostly possess the same hardware but the app adds a coefficient to the sensor's lux measurement to be similar to what you would receive with a PAR meter i.e. lux reading x .xxx coefficient= *par*. It's similar to what those online calculators do while assuming different readings based on generic Kelvin ratings(2700, 3000, 3500, etc)

Another problem is that not all sensors read higher than certain thresholds, my current phone doesn't register over 32767k lux but I have lights that read higher from a PAR meter. It has to have a par sensor to be accurate, there's a cheaper one on Amazon from Apogee but I cannot remember the brand but the USB version of the apogee is cheaper and could probably be found cheap used

Apogee SQ-420 Smart Quantum Sensor | USB Output Amazon product

 

[MIAutomatic]

Obviously others here disagree based on some of the comments, but the Photon app light meter works just fine to get a general sense of your PPFD and DLI. I use a Sun System 315 CMH with Philips bulbs, a setup for which there is a lot of PAR and DLI testing data online. My experience has been that using Photon with the paper diffuser is very effective and gives me readings exactly in the range I would expect based on the readings done by more accurate meters by others using the same ballast and bulb combo.

Is it as accurate as a $500 Apogee meter? Of course not, but it doesn’t really need to be to get the basic data you need to make informed lighting decisions.

There is a pay version of the Photon app, but the free version has all the functionality you need for the most part.

If you have not dropped your beans yet I would consider either reducing the number of plants or the size of the pots. 4 plants in a 2x4 is going to get really crowded and may create airflow issues. I would only grow 2 or 3 in 3gal pots. If you really want to do 4 switch to 2gal pots.

good luck!

Edit: I am using an iphone, sounds like android devices don’t work as well with the Photon app.