LED's, is full power needed?

[GreenVision]

Hi all, a little background info, I crossed some plants a few years back and during a large pheno hunt found a plant I absolutely love and I've been using cuts ever since. Its been a few years now and I had what I suspected were vigour issues possibly down to me taking cuts from cuts or just me... 

 

 

Fast forward to my current crop and they're looking the best they have in quite a while, I'm all but 3 weeks into bloom now and they've stopped the stretch. I think the change in soil and lights has helped them come back to life.

 

I now have 6 Lumatek ATS 300w pro LED's above a SCROG, and the LED's are currently set at 75% and about 35CM above the canopy.

 

My question.. Do I leave them at the 75% or should I raise them up a little and go full metal jacket? Would I loose any yield to only having them at 75% over the 100%?

 

Kinda stuck on this one, on the one hand I think yield will drop slightly not having them up full as there will be less light, but on the other hand if I turn them up and they freak out on me I could end up stressing the shit out of them and not only lengthen my bloom phase but possibly loose yield to stress and over lighting.

 

The LED's are pretty forgiving being a smaller unit, I think even at 100% 40cm above canopy they don't go above the recommended 1000 ppfd at all. The plants however are not so forgiving, since the off this cut has a clear temperament to light schedule and temps, not so much light intensity but when the light go out its one of those that just goes all down and instantly goes to sleep. 

 

So I suppose it does come down to yield. Obviously I want to get the max I can so will the dimming down to 75% affect the yield at all?

 

Cheers.

[Military Grade]

Depends on the lights, too high of hot spots on your par map and they can hinder the yield in that area than turning the lights down.

 

Many Growers on here don't run their lights at full power.

[GreenVision]

Well the par map on Lumateks site says that at 40cm they are really nice and uniform, plus no areas higher than 1000, which I think the max I should be at without more equipment etc. 

 

But at 75% those numbers will obviously be down so Im thinking yield should follow?

 

[stu914]

I run my 550w scope leds at 400w giving around 850 - 900 umols overall.

Returning between 1gpw and 1.5gpw, strain dependent, Any higher and the

upper leaves canoe. Sounds like you're more or less in the sweet spot GV.

ATB

[Thai Stick]

Depends on the lights but i think you will find that less can be more with led's.

 

My  Meiju 240w panels that i run 2 in a tent i have at full power, because the shitty control knobs keep failing and dim th lights to like 30% which isnt great.

On some fancy shmancy 1000w led lights i run between 50-75% because theyre super strong.

When you run the lights too strong and too close you start to see what looks like deficiencies as the plant struggles to deal with the intensity.

 

That and you wont really see the benefits of using lots of light if youre not supplementing with co2 via tank or Vietnamese worker on exercise bike in the corner.

[badbillybob]

bang them on full pelt....you know you want to.

My last run was an initial run with my new 600w leds i had them on full and the buds were almost touching the bars, only burnt a couple of tops, which were like less than15 cm from the light bars.

no canoeing , deficiencies or burning that i noticed.

 

i mean ideally you want to be around the 8-900 umol mark but sometimes life isnt ideal

 

they produced really well too.

Edited Saturday at 22:48 by badbillybob

[SkyRider]

General answer seems to be, have a play around....perhaps increase the lights slowly until you see any issues then back it off?

[Slippy One]

I’ve found that less is best. Used to get fox tails, extra pistole growth spurts, yellowing that looked like hunger and the buds at the side getting the least light looking the best so easing off the PAR works best for me. Saves a bit too, winwin 

[KC]

I run mine full whack but there are always different sized plants in there as I do perpetual. I just put the taller ones around the edges when possible like when I ran hid. Bonus of having a quantum board rather than the big bars I suppose. 

[GreenVision]

18 hours ago, stu914 said:

Sounds like you're more or less in the sweet spot

 

 

Hi ya mate, yh I'm hoping this is the case. But at this moment in time I cant say for sure. I think I'm gona have to just wing it on this grow and see how I get on.

 

It's the first full run back on the LED's, trying to get a feel for these new ones, missed the LED's actually, didn't think I would as I love CMH, but I think this is it now, sticking with the LED's onwards.

 

 

[GreenVision]

12 hours ago, badbillybob said:

you know you want to

 

I really do, I got a small gap coming up between grows (as in I cant get next cuts in straight away) so I need to maximise yield as best as possible.

 

12 hours ago, badbillybob said:

8-900 umol mark

 

I'm quite sure I'm well below that ATM. The Lumatek site says at 40cm 100% I'd be about 900 at the strongest point, I don't think the maths of dimming is exact but even a simple 25% off the 900 max I'm sitting at 650-750 tops, and Im about to go into the 4th week so its now or never I rekon.

[GreenVision]

7 hours ago, KC said:

I run mine full whack but there are always different sized plants in there as I do perpetual. I just put the taller ones around the edges when possible like when I ran hid. Bonus of having a quantum board rather than the big bars I suppose. 

 

 

Yh I loved my QB's I really did. There's an Ironic twist to that fact too...... 

 

 

 

This plant was the mother of the aforementioned cuts that I have now been growing for 3 years or so. It was an OGKZ that was just amazing on all fronts.

 

 

 

And it was grown under these:

 

 

 

 

Of all my setups over the years this one was the best. It was perfection and I've always known it was the QB's that made it that way 

 

I love the bar type lights and had just as good a result of them but there was something about QB's that just sat right with me. I even looked at them over at HLG when deciding what lights to buy a few months back, I honestly was strongly considering another QB setup.

[KC]

@GreenVision

 

That's a beast of I ever did see one

 

I do love Hlg stuff, shame it's so hard to get hold of with little to no back up if it goes wrong from what I hear. Bloody expensive too, last I looked the pound was weak against the dollar so that wouldn't have helped. They got so much choice over the pond, understandable with their market being much larger than ours. All you ever hear over here is Lumatek 

[Gsyrup]

On 28/09/2024 at 17:12, GreenVision said:

My question.. Do I leave them at the 75% or should I raise them up a little and go full metal jacket? Would I loose any yield to only having them at 75% over the 100%?

 

On 28/09/2024 at 23:45, badbillybob said:

i mean ideally you want to be around the 8-900 umol mark but sometimes life isnt ideal

 

Only you can really answer the question GV, as you're the one with all the information. As BBB said, 800 - 900 PPFD without co2 is ideally where you want to be at with your lighting. The 300w pro are a total output of 750ppf per unit at 100%, if you've got them on 75% then they're outputting about 560 ppfd each.

 

Granted, its not 100% accurate but without a light meter it'll give you a rough idea at what you're working at - (<unit ppf> x <number of units>) / <room in m2> = PPFD. If you're over 50cm away from the fixture, divide the result by 2.

 

As an approximate rule of thumb, without supplementing co2 and using active extraction, you want to be running at a ratio of 1 part co2 to 2 parts light, ambient atmospheric co2 is 450ppm.. thats where the maximum figure of 900 PPFD of light comes in. The more you exceed the final PPFD figure without the co2 to back it up, results in longer and longer of periods where your lights are on but the plants aren't photosynthesizing.

 

 

[GreenVision]

@Gsyrup Hi ya mate.

 

So with no meter, and as you say just the numbers provided by lumatek (with a little tolerance), I should be just below the area of Co2 needed for the PPFD my units are putting down at 40cm above the canopy?

 

Part of the concern was the height, where I'm in the loft I'm close to max height. I had started to ponder if because I was currently about 35cm above the canopy at 75% I may have peaked that "Maximum" PPFD you always see when buying LED's. But I do have an active intake pushing air straight across the canopy at quite a rate, so if the "standard" Co2 is 450ppm I'd like to think I am at that, and if I'm understanding it all correctly I'm good to go full pelt, in terms of light & Co2 as long as I'm above the 40cm that Lumatek did their lowest test at.

 

I think the numbers are:

 

(750ppfd x 6 = 4500ppfd) / 4.32m2 (my scrog net is 1.8m wide and 2.4m long)  = 1041ppfd???... And I'm about 35cm above canopy atm but I could up that to at most 45cm at a push. 

 

If I've done that right that's pretty close to touching max if I stay at 35cm above? 

 

 

just too add the lights do sit pretty parallel to the net, so the m2 should be pretty accurate, not accounting for lights crossing over etc.

 

Edited 1 hour ago by GreenVision