Plant to Led distance (dimmed)

I keep reading various bit about leds having to be x amount away from the plants, what the reason for this, in old money the closer the better is that not the case with Led,s?

I've got a 240w Led dimmed down to 100w and sitting approx 6 inches from the plant, will that be a problem if the temps are good?

LEDs are not created equal. Every manufacturer has a recommendation for distance

White light way different than blurple

Research your light or burn up your plants


Yer call

BobThe420Builder said:

LEDs are not created equal. Every manufacturer has a recommendation for distance

White light way different than blurple

Research your light or burn up your plants


Yer call

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I looked it up but manufacturers don't go into dimmed heights thats why I was looking for dimmed in particular.
Turns out there's no heat dimmed to 50w so the T5s are back in.

Pics and some more info would help?.... Generally the plants will tell you if you're too close, look at the tops for any signs(twisting, curling, tacoing, discoloration, etc).

Good luck

I have two 720w med grow leds literally 2 inches from the plants and they are loving it. But I'm also in week 5 flower.

Are you in veg or flower?

Are your lights full spectrum?

Are your plants stretching or are they bushy rignt now? How are they performing?

When I needed a little bit of stretch I raised them when I was happy I lowered to 24 inches above for veg.

Youre not going to get a single answer here....trust me I have tried many times lol

But like @PSUAGRO. Said pics and some.more info would help.

my question is why are you using your lights dimmed???

I've been wondering this myself. Have a Spiderfarmer 4000 with dimmer and trying to figure out if 30 inches over seedlings is with it dimmed or at full power. Currently running it 32 in at 25 percent so I guess I'll find out

Smokinnewb said:

I've been wondering this myself. Have a Spiderfarmer 4000 with dimmer and trying to figure out if 30 inches over seedlings is with it dimmed or at full power. Currently running it 32 in at 25 percent so I guess I'll find out

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30 inches??? i personally would crank it
Especially if they are over two weeks into veg

But again, like I said above not every situation is the same. I had too much bush and needed some stretch so I raised. When I got what I need it was 100% at 24 inches and mine are 720w

I always start at 100% and see what how they are responding. This whole dimmed thing sounds great if you like 50% yields...

BurntByFire said:

30 inches??? i personally would crank it
Especially if they are over two weeks into veg

But again, like I said above not every situation is the same. I had too much bush and needed some stretch so I raised. When I got what I need it was 100% at 24 inches and mine are 720w

I always start at 100% and see what how they are responding. This whole dimmed thing sounds great if you like 50% yields...

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It's just a couple days into week one. I know from watching a testing vid that at 40 percent at 20 inches puts out a par level around 600. Still waiting on my par tester in the mail( got delayed) tho

Smokinnewb said:

It's just a couple days into week one. I know from watching a testing vid that at 40 percent at 20 inches puts out a par level around 600. Still waiting on my par tester in the mail( got delayed) tho

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I don't have a par tester. Turn it to 100 percent and set it at 40 inches. Are they starting to stretch? If so lower it. No? Keep it where it is. Are they stressing? Raise it

Don't waste your money on a par meter.

Different strains and phenos may like different light.

Smokinnewb said:

It's just a couple days into week one. I know from watching a testing vid that at 40 percent at 20 inches puts out a par level around 600. Still waiting on my par tester in the mail( got delayed) tho

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you can download a free par meter for your smart phone. If the temps are good you should be ok, One thing to look out for is light stress. you would want to gradually increase your light and see how she likes it. Since it's still in week one from seed , I'm guessing I would just wait until week 2. Also pics would help.

420burn420 said:

you can download a free par meter for your smart phone. If the temps are good you should be ok, One thing to look out for is light stress. you would want to gradually increase your light and see how she likes it. Since it's still in week one from seed , I'm guessing I would just wait until week 2. Also pics would help.

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Ok. Thanks Ill grab some pics when the lights go off.

It's back under T5s and is fine now.
I had it set too high (100w) for a clone tent, i should've started with it turned right down, however we live and learn!

I'll give a few more days under the T5s then maybe try the led again.

Star Dog said:

View attachment 4707085
It's back under T5s and is fine now.
I had it set too high (100w) for a clone tent, i should've started with it turned right down, however we live and learn!
View attachment 4707082
I'll give a few more days under the T5s then maybe try the led again.

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I photo taken today, it's recovering well.

Star Dog said:

I keep reading various bit about leds having to be x amount away from the plants, what the reason for this, in old money the closer the better is that not the case with Led,s?

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The reason lights need distance is so they can spread the light uniformly over the area that you want to light up.

Uniformity of light distribution over a certain area is the only reason to hang the light at a certain height. This is a constant related to the size of the area and spread of the light.

If you want to give the plants less or more light over the same area, you should do that through dimming or boosting.

Hanging the lights closer to increase intensity doesn't really work. I will just take the light away from the edges and concentrate it in the middle under the light. ie you will create a very non-uniformly lit grow.

It's recovered nicely I'll experiment with the led at a later stage.

What's your ambient temps like? Could be the heat from the t5 aiding in the recovery vs LEDs

You never mentioned what led fixture brand you where using either, blurple is hard to grow with for starters & secondary lenses on top amplify the issues imo.

PSUAGRO. said:

What's your ambient temps like? Could be the heat from the t5 aiding in the recovery vs LEDs

You never mentioned what led fixture brand you where using either, blurple is hard to grow with for starters & secondary lenses on top amplify the issues imo.

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It's a kingbright 240w 4k
I messed up putting it in to bright even at 100w I should have started with it turned right down then gradually increased the power, when I did did turn it right down the temps went down to 18c so back to the T5s, I'm not in any hurry so the T5s are probably the best all round light for now I just wanted to test the led, it didn't go well but I'm still optimistic that it will be ideal for vegging.

Star Dog said:

It's a kingbright 240w 4k
I messed up putting it in to bright even at 100w I should have started with it turned right down then gradually increased the power, when I did did turn it right down the temps went down to 18c so back to the T5s, I'm not in any hurry so the T5s are probably the best all round light for now I just wanted to test the led, it didn't go well but I'm still optimistic that it will be ideal for vegging.

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cannabis seedlings outdoors get 2000+umol/s...... 240w of 4000k mid power diodes should have no issues vegging

18c is too cold for optimal results, LEDs still have cons, this is one of them.

Star Dog said:

It's recovered nicely I'll experiment with the led at a later stage.
View attachment 4708827

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The day after tying...