Have a question about DLI

I have a lighting question. So I have 2 cheap lights and I have 260 true watts together. I have grown my girl at 55 DLI for most her light. But I just seen the chart saying autoflowers are to be at 45 DLI tops (no co2). So I was able to turn my lights down to 60% and only lost 5-7 DLI ?? Does that sound trustworthy ?? Also would you just keep her where she was, at 55 DLI ???


Pour on the light if she will take it.


I personally go with 50 - 60 until later in flower where I go to around 45.

And if you are using the Photone app to measure I would trust the readings.


I am using Photone. And ok I’m in week 4 of flower. About when should I dial it back to 45 DLI or so ??


When she starts to look mature - your girl is building buds now. You have a way to go.

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I stay around 45 in flower but have gone to 60-on a few that loved it. Foxtails, a sun burned look (bleaching) or leaf curl will let you know if it’s too much :love_you_gesture:

I am having a hard time trusting the apps. I have photone, and tent buddy, and they both read different. I use an android phone, and set photone on full spectrum led (hlg 350r), and 4000k on tent buddy. Photone always reads less than tent buddy, and the angle you hold your phone makes a big difference. But I can’t afford an apogee.

Make sure in settings you have your light on time in hours set correctly or your DLI reading will be useless. Also running a high DLI is pretty much useless if you loose control of VPD.

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Hey guys so I just noticed a few leaves are yellowing and was wondering y’all’s opinion. The plant seems healthy other than about 4 or 5 leaves.

@Dexterado @Fiz @MidwestGuy @OGIncognito @Blastfact

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Don’t worry about those lower leaves. It’s normal for the plant to shed them as it matures.


How did you arrive at this number? If you stuck your phone under the middle of your light and it read 55 dli this is not now how dli is intended to be used. You need the ppfd average of your entire space in terms of actual umols/s/m2, not just from a single point where photon density is the highest.

Chances are your dli is not this high. Not to be shameful, mine isn’t either on a 12 hour schedule. I max at about 40, and its more than enough light to grow hard buds. The reason i don’t run any higher than this is because the ratio of increase in productivity falls off in comparison to the amount of light provided and energy consumed to do so.


Ohhh okay. Yes I just put my phone under there and that was the read. Can you dumb down the equation for me so maybe I can try and measure it ???

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Once you have ppfd average there are calculators you can plug into online. If you have ppf of your light is simply ppf/area in m². This is theoretical ppfd average, but it’s close. Otherwise you can plot your grow space equally taking series of measurements from side to side and front to back then average them. The more spots you plot the more accurate you’ll be.


So I don’t need to be spot on because I’m getting a new light soon but I wanted a ball park number.

So at 14” above canopy I took 5 measurements of my DLI l, then adding them together, then divided them by 5 and I got an average of 35.6 DLI. You think that’s probably a little closer to my average ?? @dbrn32

Where did you take measurements from? If you took from center and maybe all 4 corners results may be semi accurate.

The idea is to capture the entire canopy so your highest points are offset between your lowest forming a true average.

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Yea I took them from middle front back and sides

Hears a example of measuring out my current Baby Shark Auto grow. It’s not a good example because it is a complete natural grow. And presents problems for a DLI measurement because of the radically uneven canopy. My Apogee meter does not calculate DLI, so I take all the measurements, add them up, then divide by the number of measurements for my average ppfd. Then I go to the HLG DLI calculator on there website. I put in the average ppfd number and the number of hours the lights are on in a 24 hour time period. Which is 20 hours a day for this grow and click on convert. That gives me a DLI number of 38. If I only measure the two tallest bud sites I have a DLI of 43. Normally I don’t take numbers at the front of the grow because the tent door is open and this will produce lower numbers than measurement taken at the back of the tent on buds taken at the same height and space in the tent. With the door open your numbers are lower because you loose the reflective properties of a zipped up and closed tent door. Ignore the leaf damage from a massive nitrogen spike that about killed the plants.