At a crossroads. My DLI reads 40 when the light is about 12 inches from the canopy. I’m thinking I should have the light around 20 inches. What should I go with?
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What light do you have?
How are you determining DLI?
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Spider Farmer sf 1000d and a Photon app
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Based on the 12" PPFD map the lights average PPFD over the area is 506 yielding a DLI of 33.
I do not use the photone app. If its properly filtered I suspect the high DLI reding is based on the location of the phone. ie more toward the center. Also the number of light hours affects DLI. A PPFD of 617 yields a DLI over an 18 hour period.
Are you wanting a lower DLI because of the the plants age & size?
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I feel your thought with the DLI, I have to be 3 inches from my scorpion rspec at 500w+ to get 40dli using a s22 ultra samsung. Not a big believer in the app. 
I go with my gut feeling sometimes it works, sometimes it doesn’t.
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I couldn’t get over 47dli with my 350r maxed and my s22 like 6" from either board, using Photone app. Using my Motorola Edge+, the ppfd tops out at 820 on the Photone app. I can adjust the light, watch it get much brighter in the grow closet, and the numbers on the app will barely move. And they top out. I can hold the phone in one spot til the numbers stop, move it and put it back in exact same spot and the numbers be way different. I’ve basically just been eyeing it the last few weeks.
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I’m a newbie. I’ve heard 40 is a safe bet. But when the light is 6-12 inches above the canopy and reading 40, that makes me a little skeptical on the app.
I personally use the photobio LGBQM2. Runs about $180 on amazon and it measures in a few outputs but i mainly use umols. If money wasnt an object i would of got the apogee as they run about $560. As for dli i have never used the photone app as ive always used my handheld to get readings. Hasnt let me down yet
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Are you using the printer paper they recommend for the diffuser @Lightyear. Migro on YouTube did a study and the wrong paper can make a big difference. I got lucky cause my wife is using the paper they recommend.
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@TLC @Borderryan22 @Lightyear I found with my S22 ultra I had to calibrate the app to my lights par chart. Go into settings and there is a calibration mode. I calibrated at 12". Moved the phone to the center point of highest reading I could get on a stable surface in tent. Then hit calibrate and enter your lights center par number. Now when I lower my phone it matches my lights par chart. Just make sure you have a reliable par chart. Some smaller light companies I’ve read inflate their numbers.
Also with Samsung you dont need the diffuser.
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I recently have been discussing the photone app on my journal.
It can be accurate if it’s calibrated within reason. The people who made it won’t discuss accuracy just downloading it. Which means you need a meter to calibrate it, or you put your trust in the par maps provided by the manufacturer of the light to calibrate it… 3rd party is usually better… however when these tests are conducted there are no shadows or voids in the tests, so even being close to the reflectivity of the testing area can distort readings. Tent ‘door’ zipped or open can mean 100-200 ppfd points lost.
But readings can vary from phone to phone, not just camera to camera iOS to android.
I’d recommend hanging your light at recommended distances until you want to get technical enough/involved in growing enough to buy a meter.
I relied on photone for quite some time before getting an appropriate ppfd meter and the numbers are different. Not just with my phone iPhone 12 Pro Max, but the wife’s iPhone 13 pro and the meter.
iPhones best bet for paper diffusers is 22lb paper, which is hard to find and 22lb paper is more inconsistent then any other weight, so your accuracy could be different based on brands…
See where I’m going with this?
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I’ve been using an Apogee meter that gives very accurate readings. I need to download the Photone app and see how they compare. The are some spectrum on the ends that Photone does not capture. Phone cameras are designed to capture the spectrum perceptible to the human eye. Plants see a wider spectrum of light than a phone can measure.
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I would, I compared. I don’t use apogee I use Photobio which is almost as accurate as apogee just no accessories available. The difference for me using 20lb paper (recommended by photone) on my iPhone was 100 points or. 100 points higher on the photone app than the actual meter.
EDIT
The readings here are different on the meter because of where I was at the opening of the tent. I have to zip past the lights to get a more accurate reading. The fluctuations are not what matter, but the differences between photone and ppfd meter.
side note
I use this simple calculator to translate my ppfd into dli
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@Low Is this straight downloaded or calibrated to lights par map?
I know you have the meter but maybe calibrate it to your manufacturer light par map and compare.
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Straight downloaded buddy, par maps represented are different than the par you will get at home… truly there isn’t a convenient way to calibrate them. Same with efficacy… they all post total numbers not useable numbers. Rabbit hole…
Photone recommends calibrating them with a “reliable device.”
I’d honestly recommend a meter… whether ppfd or lux, lux can be converted to ppfd, then converted to dli, and they are cheaper.
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ANdroid app maxed at 33K lux, in or out.
UT383BT maxes at 100Klux, outdoors.
will decrease if closer that 15 inches from light.
I can get 50K lux from HLG 350R or Vipar Spectra V 1200 (200 and 500 watts respectively), at 25 inches canopy.
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I have seen several graphs giving DLI for various growth stages. This one is the most common I’ve seen and saved.
Don’t get too carried away with technical aspects. DLI is informative but I have never worried about it. I have good lights and I let the plant tell me if it is happy or or not. I adjust the height accordingly and dim if necessary based on stage.
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The tent buddy app gave me more accurate readings I believe. The photone app didnt seem to read right on my s22 ultra either.
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@beardless had a great point here. Let the plant tell you want it wants. Iv had some plants love 52DLI and other much less.
The plant will tell you all problems but knowing how to read that takes time.
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DLI is not really an important measurement when growing indoors. Optimal photon density for peak cannabis photosynthesis is between 500 and 700 µmol/m2, And anything over 1000 PPFD can cause damage with ambient CO2. . So you want to get all the corners of the tent as high as possible without getting the center over 1000. If your light produces enough PPF and run it at 18-6 followed by 12-12 for flowering the DLI will be fine. The only reason to worry about DLI is if you are out doors and you aren’t getting enough sun.
If you wait for negative responses to show at the very least you have lowered your grows efficiency and at the worst damaged your plants.
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