LUX and seedlings

These are two Purple Kush fem… I could identify their cotyledon leaves on 2/16. Today is 2/18
They are under a 65W Chilled Growcraft X1 Mini set at 14". It has the veg spectrum. I used the trays cover with the light at 100%. I am removing the cover so the question is this too much light for them at their young age

I am thinking 23300 might be a little too much.
I thought I read seedlings should be around 7000.
I have backed the dimmer off and the meter is now 9500. Have to push them a little


Nice, I have 2 seeds getting ready to plant. 1 Blueberry ILGM auto and 1 Amnesia Haze also a ILGM auto. I’ll be watching.

I never really thought about it before. But, since I have the meter I might as well use it rather than guess.
I have grown both as autos too. Loved the blueberry. They were tight, compact and easy with no issues. The amnesia haze on the other hand gave me problems of my own making. Novice mistakes like not phing in and runoff. Over fertilization and calmag deficiency. Other than that they did great. Actually, once I got things squared away they were very nice plants and fairly heavy producers.

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I have a lux meter on my phone still trying to figure it out. Lux to PPFD to DLI Nicky was helping me out with it. I love the Blueberry. the Amnesia haze was my first plant I grew a year and half ago. lot of problems all my fault Lighting (T5 HO florescence) Phing, nutes all beginner mistakes. with some help from @Nicky i was able to finish her. Got maybe 3or4 grams off her LOL.

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It all sounds familiar. Time frame is similar too. I started my first seeds 8/2019. I seem to recall some of the PPFD DLI discussions. I know Nicky has it down cold. Ppfd x (3600 x your light hours) / 1,000,000 = DLI. The tough part is converting LUX to PPFD based on the light’s spectrum


I would be hesitant to give anyone an exact math equation just due to the fact that light spectrums are different as you stated above @beardless.
I use waveform lighting converters unless hlg then I use the HLG’s converters.

Here is a chart though to help, the red mark is mine. I dial them back down once I see fox tailing in the last 2 weeks it usually shows. Some plants can finish without fox tailing though.

I use the HLG converter. my light is a HLG 260 QB 3000 V1

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The red line works for me. I would have thought the recommended DLI would be higher during flower than shown. But, that is probably where my lights are at. Have not really tried to figure it out.
Chilled publishes its PPFD maps for its lights at quite a few different heights. I will have tp play around with it for kicks. It doesn’t take much these days. :sunglasses:


@Nicky DLI question if you please.
As I previously mentioned Chilled publishes the PPFD maps for the light I use. The maps are at various heights covering a 2x4 area. Along with the individual point PPFD it gives the average for the entire area. Me being a number cruncher at heart I recalculated the mathematical average given. My question is. I have 2’ x 2’ tray of seedlings / clones, whatever, and the tray is centered under the light. To be more accurate in calculating the DLI of that tray’s area, I should be using the average PPFD for that area and not the entire footprint.
Example using the formula PPFD X (36,000 X light hours) / 1,000,000 = DLI
2x4 average PPFD 184, 18 hr light cycle = 119 DLI
2x2 average PPFD 242, 18 hr light cycle = 157 DLI

I also assume, the reduction in watts consumed has a linear reduction in PPFD and DLI. Meaning, if I dim the light to 50%, its PPFD and DLI will be half of the above amounts.

@Deepsix to continue the discussion.
@dbrn32 if you have anything to add
thanks to all

Another question at 3:30 am on a Friday morning.
Two 2x4 rectangles representing the light’s total footprint. One outlined black the other in red
The lights are set so there is 12" overlap represented by orange.

As you know, a light’s PPFD can drop off significantly at the outer boundaries of its footprint.
The average PPFD of a single light in the overlap area is 125. What is the PPFD for this area when both lights are on? 250?

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I am going threw this myself…(did recently and touch on it again every once in awhile)
I am always up for some nerd talk about lighting so here i am.

If it is not, im am anxious to hear why. Mine are set to overlap but they move in opposite directions…im wondering if im keeping my lights far enough from the top and close enough from the bottom (most of witch is in my overlapping area)


Personally, I think you are wasting your time trying to calculate dli for seedlings.

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Your missing a period.
11.9 DLI is for your 184 by 18hr
15.68 DLI is for your other one.

Use the average of the area your growing in.

I generally agree with this

However it is nice to sort of have an idea and some notes on hand.
I personally have a set some lux notes for seedingly state veg stage and min /max for bloom stage.

However I tend to tell people to dim their lights and control stretch via light strength as this is a good way of reading the plants.

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Just doing as an example. Yes go for bigger fish

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Sorry brother that is above my pay grade. I’m just learning about it

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You should be most worried about dli with full canopy. With that, use the ppfd average to calculate dli.

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The formula should use 3,600 (seconds in an hour) not 36,000 as above.