DLI from sf4000

Hi friends, have any of you with a sf4000 checked the DLI? Mine at 100% was just over 29 if I did it right. I wasn’t able to use an apogee, just phone apps. I was expecting more tbh mainly because I thought I’ve damaged from light burn intensity


Which app are you using? And in the menu for your app did you choose the light source also the hrs of exposure. These affect the numbers

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These are the 3 I tried. For calculations from lux to dli I used waveform

I’m pretty sure I used the lux and the ppfd meter correctly as far as light and hours. I couldn’t figure out the light meter… but I didn’t try real hard since I got similar results on he other two. Since the two were similar, it leaves me wondering about the lightScreenshot_20210829-233943_One UI Home

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This is the recipe for DLI

Ppfd x (3600 x your light hours) / 1,000,000 = DLI

At 500 ppfd … 500x (your 18 hours x 3600 = 64,800) = 32,400,000 / 1,000,000 = a DLI of 32.4

You multiply 3600 because it is the amount of seconds in one hour… and divide by 1,000,000 because it is the number of micromoles per mole

I use 500 ppfd as an example because it takes 30 moles to grow quality buds and 500 is a good round number to shoot for as a min ppfd and it gets you above the 30 m min @ 32

I’m thinking that you might be getting an off ppfd because you have it set for 4000k the app I use has a natural daylight 6500k setting and I was told that at that setting the app was most accurate measuring led but I don’t know how close most accurate is :laughing: I’ve messed with it a little I has another setting for red…blue…and white I get the same readings as the daylight setting :sweat_smile: …some day I’ll get off my wallet and buy a meter but I’m not convinced 500 bucks is worth knowing my ppfd.
Hopefully this helps you out… I finally got tired of stressing about the numbers and went back to growing

Edit = I just wanted to add do the math on the sun outside my app reads 2000 ppfd in my back yard where I have a happy little plant not burnt at all

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I use ppfd meter but didn’t work until I changed the source type to the light I am checking white led vs hps also I think the device your using as some phones have great light meter for the camera and others less quality. The phone I’ve been using is s21 Galaxy.

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I wonder the same thing about my phone it’s a Galaxy A21…

I saw the numbers in the source selection menu… my brain went straight to watts (sf4000…)… not color temperatures duh :roll_eyes: :sweat_smile::rofl:


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I was looking at the source numbers as watts not color temp… duh :rofl: I really need to be led to the water sometimes

I’m not really worried about the numbers other than to understand, somewhat, my lights limitations and capabilities

3rd grow now with this light (seeds just came of dirt) On my 2nd grow i burnt one at 4-5 weeks from getting too close. It never really recovered. From then on, no matter the distance, every time I cranked lights over 70% i had problems. Im sure I have other issues but I wanted to understand how much light the plants can handle at different times and what light can produce…

I should do the math myself. Who knows if the online calculators use the same equation. Im guessing they do :man_shrugging: Your explanation of it though was as good as Mr Bigbee’s. Thanks

I think I know some of the other things that went wrong. Im adjusting my jack’s formula a little. Using more mag. Also going to continue fertilizer longer through flower. I think I started flushing too early and the HF soil was shot. Im also replacing my bloom fertilizer with a monopotasium fertilizer and again adjusting my jack’s schedule. Im also thinking about getting a small humidifier since my RH hovers around 35%

I got good bud 2nd grow, (gorilla glue was fire but girlscout sucked) they just seemed to stop growing (or I killed them with lights) before they were 100% mature. Trichromes were moving really slow towards amber at that point and I thought the plants were dead in dirt so I cut them a little earlier than I like. I like the couch lock :laughing:

I’ll get up to my tent and take another stab with source at 6500k and check the math myself.

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You might have just run into a sensitive plant, some can just fight with you throughout the grow I’ve learned to use the lower intensity areas under the light to my advantage. If you look at the numbers in a ppfd map the center is always the highest and the sides are lower and corners lowest. If I have a sensitive or taller plant I put it in a corner while I put my shorter plant in the middle because obviously it is further from the light being short

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I didn’t really explain that well… sorry.

While the gsc got burnt and stunted, the other 4 showed slight burn, but seemed to recover quickly. I had 3 gg and 2 gsc. When I cranked the light over 70 the whole grow suffered. The 2 gsc took it the worst, 1 never came back, but the other gsc was more sensitive than the gg

Soo… I think even though they didn’t show it, the whole grow was messed up… idk

I’ve got 3 gorilla and 2 Northern lights this time. Im definitely going easy on lights. I’d like to run them high during veg, then drop down at beginning of flower and increase a bit at a time throughout flower. I learned that’s a good way to keep plants from stretching too much while getting good harvest. I have this

Photosynthetic photon flux density can’t be calculated without knowing the size of space that it’s in. Since ppfd is critical in dli formula, same light will have different dli in different sized spaces.

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It’s a 5x5x8 so 200 cubic feet 25’sq It’s not quite 8’ But I don’t know where that would be in the equation or where to enter it in the app. Is that something I would need an apogee meter?

I found this. At least I could kinda calibrate with it I guess

Except it’s for a 4x4 tent and mine is 5x5

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Doesn’t this imply that the siding of the space also impacts DLI, whether or not the walls absorb or reflect light?

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Are you trying to get par / ppfd values. The phone and the application being used makes a big difference. Migro did a comparison of IPhone and Android apps. In a nut shell Android apps were the least accurate. The Photone app on IPhone was very accurate. The title to the article is
PAR meter APPs tested & compared for accuracy


Thanks for all the info guys been reading along and trying to figure this out. This is what I’m trying to figure out, or already a ruff estimatement. I have 2 lights, take the average PPFD of both, divided by 2 then use that ppfd to calculate? Running both around 18 inches sf 413 xs 700 / 2 551 PPFD average ? DLI 35.6 lights on 18 hrs that right ?

Just a side note: PPF, PPFD, PPF/W metrics measure only [photons] (Photon - Wikipedia) within the PAR range. These metrics are limited to PAR range, however there are benefits of light outside PAR range (400nm to 700nm wavelength)

Also these metrics do not account for quality of light spectrum. It is important to look at spectrum along with these metrics for a complete picture.

A full spectrum lamp at 2.5 PPF/W will greatly outperform a 3 PPF/W lamp that has only only Red + Blue photons

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Sorry about the typing errors auto correct, so as soon as I think I’m starting to figure out you pull out all that out about par Ppfd PPF PPFW ? Idk what to think, I’m new and the more I read the more I get confused

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…and this


Thank u so much @MH47 fun read lol, Im new in first grow so I am just winging it, nice to have something to help guide. 1 question I have autos so same principles apply to a certain degree, but I’m running 18/6 in week 5 with what I think are pre-flowers but idk, so 12/12 would not benefit me ?


Correct. Just leave autos on 18/6. Cheers!

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