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This is what LED Light burn looks like...

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This is what LED Light burn looks like...

OntarioGoldenHash 20 Replies 5,432 Views
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OntarioGoldenHash

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#1
For the benefit of the forum.

I had a plant that started really slow compared to the others, so I throw it in the tent as well.

This is the result of the LED light being too close and/or being too bright.


This is the LED, what I consider to be the best on the market when purchased: https://www.hydrofarm.com/p/photobio-mx-680w-100-277v-s4-spectrum-w-iloc/ptb7680ls41

3rd Party review of the LED vs other well known brands: https://s3.amazonaws.com/hydrofarmpubdocs/Phantom PHOTOBIO LED PPI v.May2021.pdf

Anyways back to the issue I am facing and trying to fix, and hopefully others can learn from.

From a previous post of mine had me thinking it was due to lack of potassium, I was corrected and its due to light burn.

This is a picture from this morning, we can see the upper leaves are really showing it and even turning purple from trying to protect itself from the LIGHT.

Light had been moved to 80cm/32inches from canopy, and the PPFD is 435 and DLI is 38.

20220904_093711.jpg
 

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#2
The ppfd isn’t that high, but that DLI is up there. You getting that with 12/12?

If so either the ppfd or DLI readings are off.
 
#3
freezeland2 said:
The ppfd isn’t that high, but that DLI is up there. You getting that with 12/12?

If so either the ppfd or DLI readings are off.
Click to expand...
This is the new settings I am trying, previous to this the lights were lower and brighter. I am trying to find the right height for this light and my setup, whilst not trying to burn nor under light them.
 
#4
Thats too bad, but it will recover and I have high hopes for you that those burn spots indicate where the resin rails will form on new growth.
 
#5
freezeland2 said:
The ppfd isn’t that high, but that DLI is up there. You getting that with 12/12?

If so either the ppfd or DLI readings are off.
Click to expand...
I noticed that PPFD readings differ when the tent is open versus when the tent is closed. I use a phone app so I have to hold the phone when I'm taking a reading. I think my arm and hand also affect the reading. My theory is that reflections matter. So now I keep the tent as close to the normal growing condition as I can. That just means I put my arm through the smallest gap I can.

I don't use the PPFD readings very often, however. I mostly just go by how well the plants are growing.
 
#6
BigBlonde said:
I noticed that PPFD readings differ when the tent is open versus when the tent is closed. I use a phone app so I have to hold the phone when I'm taking a reading. I think my arm and hand also affect the reading. My theory is that reflections matter. So now I keep the tent as close to the normal growing condition as I can. That just means I put my arm through the smallest gap I can.

I don't use the PPFD readings very often, however. I mostly just go by how well the plants are growing.
Click to expand...
An open or closed tent definitely effects the ppfd with all that reflective material in a tent. It’s why it’s there.
 
#7
Something is still wrong with your PPFD or DLI conversion. Using your claimed 435 PPFD and the HLG calculator I'm coming up with a DLI of 37.81 and have to use 24 hours of light on to get it. Other calculators online are showing 37.58 to 37.90,,,, something is wrong. Either you have a bad PPFD reading or the DLI calculation is setup wrong if your running 12/12. By most DLI calculators at 435 PPFD with 12 hours of light your DLI should be around 18.6 to 18.8......
 
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#8
Blastfact said:
Something is still wrong with your PPFD or DLI conversion. Using your claimed 435 PPFD and the HLG calculator I'm coming up with a DLI of 37.81 and have to use 24 hours of light on to get it. Other calculators online are showing 37.58 to 37.90,,,, something is wrong. Either you have a bad PPFD reading or the DLI calculation is setup wrong if your running 12/12.
Click to expand...
What he said ^^^^^
 
#9
If a plant has a slight Mg deficiency, the burn looks a bit different.
 
#13
freezeland2 said:
True, but if one cites numbers and they obviously don’t make sense based on the info provided the OP should be informed. We are all here to learn, just trying to be helpful is why I pointed it out.
Click to expand...
Galaxy S10+

Light is 30inches away at 70%, because they were getting burnt before.

Looks like PPFD Meter app DLI is way off, thanks for the tips and pointing it out.

'PPFD Meter' app below

Screenshot 20220904 153141 PPFD Meter



'Tent buddy' app below

Screenshot 20220904 153113 Tent Buddy
 
#15
Blastfact said:
Are you really running your light 20 hours like a auto flower?
Click to expand...
Why not? Vegetative growth is vegetative growth.

whats the difference between photoperiod vegetative growth and autoflower vegetative growth?
 
#16
If your wanting to develop a good DLI number PPFD needs to be semi accurate and duration of light on time is a data point. Plus those plants are in flower. So are the plants photos or autos and what is the true light on time????
 
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#17
Blastfact said:
If your wanting to develop a good DLI number PPFD needs to be semi accurate and duration of light on time is a data point. Plus those plants are in flower.
Click to expand...
Then they must be autoflower…. No? How else would they be flowering.

ppfd over time is DLI but like i said plants dont care about numbers. Too many variables that effect this. These numbers we are so concerned with being exact are nothing kore than rough guidelines.

The benefit to measuring them is to replicate it in future grows… they are just arbitrary numbers that give reference not rules
 
#18
Plant is on 12/12, they are photo dark angel. On Week 10 ready for chop tomorrow.

Not this plant, but my others.
 
#20
@OntarioGoldenHash go by your plants and record the ppfd and photoperiod time. that way you can replicate your previous reaulta and evaluate future changes to see if they are beneficial or not.

the more light a plant can handle the better the healthy generally speaking
 
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