Lower Lights vs. Dimmer Switch?

[bluter]

Most professional installations I see the leds way up high unless it's for shoots or so, but then of course the whole ceiling is plastered with them.

with led you want the light as wall to wall as possible. it's one of the reasons quantum boards and strip rigs have taken over from other designs.

I was thinking about bounce though as now I've scrogged wall to wall with a LED and had very poor penetration as I had a bunch of albino buds underneath not being able to do photosynthesis versus the most well round buds I ever grew was in a 1x1m tent where I only had one plant in the middle with a HPS above it, there all the buds were very well formed all over & under the base of the bud was really fat and then a big top grew out of it, now my tops are fat but it gets slimmer down the branch as the canopy gets very dense.
So you kinda don't want to use the entire space but a gap wide enough for light to bounce sideways into and underneath the plant and the distance of the wall just in the sweetspot for a boosting effect of the lights.

the bounce is limited because led is so directional. bounce is limited. wattage becomes a determinate factor in led, moving higher on the 35 - 50w per sq/ft recommend will result in greater penetration.

it gets tricky when investing in a rig as efficiencies have gotten better over time, dropping the wattage needed. my old cob rig needs the upper end of that 50w, a newer strip rig with decent components will perform as well closer to the lower end.

unfortunately, the efficiency is tied to the quality of the components, and there is a very wide range of quality across a multitude of mfgrs. growers really need to educate themselves on lighting now more than ever

 

[Fenderbender]

That's why I was looking would going to Cobs with reflectors or lenses, or going to something like a Sanlight EVO or a 4Twenty led system that both have optical lenses improving the beam angle be a help? I'm looking for a more all round energy distribution (less efficiency hooray ) as with the regular led board when close to the crop the flower under the left side of the board doesn't really benefit from the light coming from the right side, a bit more at height but it still very much a top down situation.. if one were to hang two HPS lights next to each other you'd see a lot of shadows disappear or shrink.
The EVO fixture would definitely be an improvement as I get 4 lights spaced out evenly with 10 cm to each side of the tent left, and In depth they are spaced out as well more evenly, it would be like getting 8 smaller lights.

 

[bluter]

That's why I was looking would going to Cobs with reflectors or lenses, or going to something like a Sanlight EVO or a 4Twenty led system that both have optical lenses improving the beam angle be a help?

lenses only cut your intensity and penetration. passing through any lens cuts 25% or more photons from reaching the target.

lenses only do two things, they make led even tighter and more directional that it already is, or splay it out. in either case it reduces intensity while doing so. i stay a thousand percent away from rigs that use them. in most cases the lens is not there to improve the light, it's there to protect the emitter.

I'm looking for a more all round energy distribution (less efficiency hooray ) as with the regular led board when close to the crop the flower under the left side of the board doesn't really benefit from the light coming from the right side, a bit more at height but it still very much a top down situation.. if one were to hang two HPS lights next to each other you'd see a lot of shadows disappear or shrink.

two hps in the correct configuration is much greater than a single hps of the same combined wattage. hps has a doppleganger effect that is not quite the same in led. you're chewing through piles more power to get there though. that's always the advantage to led.

The EVO fixture would definitely be an improvement as I get 4 lights spaced out evenly with 10 cm to each side of the tent left, and In depth they are spaced out as well more evenly, it would be like getting 8 smaller lights.

a lot of the newer led systems are designed to be daisy chained to make use of that situation. for most home growers in a 2x2 to 4x4 space it's overkill or simply not efficient. it's an advantage in larger spaces though.

 

[Fenderbender]

Well yes more splaying out sure at a reduction I guess, I would still need to dim the light anyways despite reduction of lens and the system measures higher efficiency than most others on the market so I don't know if that really matters if it's lensed or not. I'm guessing that's factored into performance.
But I need more light at an angle as I'm sure this will improve overall formation and uniformity.. the other option is to grow less buds and more open to get the desired result, but well..

 

[bluter]

Well yes more splaying out sure at a reduction I guess, I would still need to dim the light anyways despite reduction of lens and the system measures higher efficiency than most others on the market so I don't know if that really matters if it's lensed or not. I'm guessing that's factored into performance.

it won't be. the figures cited are always without lenses with the led running max wattage, which is typically 50% higher than what the final driver runs the emitters at.

But I need more light at an angle as I'm sure this will improve overall formation and uniformity.. the other option is to grow less buds and more open to get the desired result, but well..

the best option is to grow the top of the canopy and tailor for that. led actually produces more than hps / mh now under a fraction of the wattage, if you have a decent rig. you have to know how to grow with them though. it's a different animal than hid.

 

[BadBeerBreath]

I was surprised by how low his recommendations are for DLI values. In the same way that the folks at growlightmeter.com have zero research for their recommendations, I haven't seen or heard of any research that Shane uses to support his recommendations. However, he has geared his products to support those light levels so I'll give him marks for consistency.

The light saturation point for cannabis is 800 to 1000 µmols and cannabis can be grown under 24 hours of light. My past three grows were autos and I ran them using 18/6. As far as the plant is concerned, there's no need for that. My current grow, germinated 9/1/22, was going to be 24/0 but I checked my electricity bill and discovered that my rate per KwH was 61¢ between 1700 and 2000 versus 34¢, so I went to a 20 hour day with the lights off between 1730 and 2030. That'll save me $250± per grow so I made the change. Were the cost of electricity level, I'd run 24/0.

Re light cycles - there's nothing that cannabis does during lights out that it doesn't do with the lights on. The "dark cycle" is a complete misnomer, the real name being the Calvin cycle.

Re. DLI's - Bugbee's most popular video and the paper by Chandra illustrate that the curve for net photosynthesis (Pn) starts to roll off when PPFD > 500µmols. I assumed that Pn was a proxy for yield and accepted that, even though it's not a linear relationship, the electricity bill would be higher but at least I'd be getting more weed. That turned out to be close but not quite on target.

The key point is that we're not harvesting photosynthesis, we're harvesting (well I'm harvesting) cannabis flower and the good news is that, while Pn is not linear, it turns out that plant yield, crop yield, and crop quality are linear meaning that the more light you give cannabis, you get more growth from the plant and the ratio of flower to inflorescence increases. Refer to the Bugbee video about indoor hemp production - it's extremely informative about the relationship between DLI and yield, as well as a host of other issue. There's other research that confirms Bugbee - I can find the cites if you're interested.

I'm a believer in "big light" but I ran "regular" levels for a couple of grows and, sure enough, everything turned out fine. About halfway through the third grow, after watching a DeBacco video for the Nth time, I decided to "turn it up to 11". Check the grow journals at the links and you'll see how things turned out. My light levels for my current grow are below. The DLI's are for the average values from the two plants. The only time I've seen any evidence of too much light is when some of the PPFD values were well into the 950 - 1050 µmols range. At 850 to about 950, this strain is doing quite well.

Again, running autos at a DLI of 40 moles or gradually ramping up light levels will get a very acceptable crop but there's no particular reason to limit your yield by sticking to those light levels. Per Bugbee, a lot of his clients are leaving a lot of money on the table by not giving their plants high light" and, as long as the rest of the grow is squared away, cannabis will click right along at DLI's > 60 mols.

and a family portrait:

I take it you don't worry about (obviously) dimming (or raising) lights in mid to late flower then that's suggested by many, including growlightmeter.com?

Anyone with thoughts on that...dimming late flower?

edit: Sorry, just looked again at your chart. Looks like you do reduce light then. Still, would be interested to hear yours and anyone else's thoughts on dimming mid flower.

 

[ExNavyInSTL]

This was the first I had heard about reducing intensity by dimming the lights or raising them in late flower.

 

[Delps8]

I take it you don't worry about (obviously) dimming (or raising) lights in mid to late flower then that's suggested by many, including growlightmeter.com?

Anyone with thoughts on that...dimming late flower?

edit: Sorry, just looked again at your chart. Looks like you do reduce light then. Still, would be interested to hear yours and anyone else's thoughts on dimming mid flower.

growlightmeter.com and Shane at Migro strike me as being very conservative. Many light manufacturers recommend pretty high light levels as do other sources but they don't differentiate between photos and autos. I haven't run into problems with autos at 900 and I frequent another site that's auto-specific and there's no mention that autos can't handle that level of light.

As you've seen, I will drop DLI/PPFD if the plants are reacting negatively to the light levels and, IIRC, I dropped light levels when I had an Mg deficiency because Mg is needed for photosynthesis and I wanted to reduce the odds that a problem would occur.

Other than that, my thinking is to stay on track for 900µmols. I take that approach because research has shown that more light results in a great yield and a higher quality crop, assuming there are no other limiting factors. If there's a demonstrable advantage to changing DLI to increase crop quality or yield, I have no qualms with changing my growing practices, assuming it's practical and cost effective of course.

 

[BadBeerBreath]

That's really great information, thanks a lot.

The anecdotal information on this topic is not hard to find, it's generously scattered across the grow forums and elsewhere of course, so it's nice to come across someone who's already aggregated a lot, and put it to well informed practice.

I've been growing a few years, but only just over a year now indoors so I'm still trying to gain as much solid information as I can. As mentioned up above, sure you can have a decent harvest growing at 40 DLI, or doing this, doing that, but it's nice to know when you are providing best practice that we know.

You've helped me tonight decipher an issue in my current grow. I've only one plant growing, a Mango Smile auto that's now approaching late flower. I've been running lights as high as 50 DLI, currently 45ish, but noticed she's been fading a tad early, showing some mag deficiencies. So what you were saying makes so much sense. A little too much light might be the cause of the early fade. I'll keep an eye on her for a few days, then may reduce further if fade gets worse.

 

[Jaz]

Shane at Migro strike me as being very conservative. Many light manufacturers recommend pretty high light levels as do other sources but they don't differentiate between photos and autos.

From the a vid:

Photos - light period 12 hours - 900 µmols/m2

He states for 1000+, supplement with CO2

Autos - light period 20 hours - 550 µmols/m2

j

 

[Delps8]

Thanks for posting that.

I had my "autos" blinders on…. :-(

900 is great and about well into 800 - 1000µmols range for the light saturation point. What got me was 550µmols for autos. That's a DLI of 40 moles. Perhaps he's tying it back to the DLI of 12 hours 900µmols (39 moles)?

I don't think I've seen any other source recommend that amount of light but at least he's broaching the topic.

What's interesting is that he's worked with Bugbee and he designs grow lights so I suspect that he's read much of Bugbee's work and Bugbee's philosophy yet he's so conservative.

 

[Jaz]

What's interesting is that he's worked with Bugbee and he designs grow lights so I suspect that he's read much of Bugbee's work and Bugbee's philosophy

Yeah, I've seen quite a few of his vids where he's interviewing Bugbee or has Bugbee in the vid as a guest speaker.

In another vid he's at a cannabis farm, can't remember if it was with Bugbee but he's going right to the source and getting info from the right people who are successful at growing.

yet he's so conservative.

He's always posting about efficiency and I've even seen him include a price range, how much it would cost you to run per year, (subject to a rate per kWhr) so I guess he's looking out for the price conscious grower. You don't want to waste electricity if it's of no benefit right?

What got me was 550µmols for autos. That's a DLI of 40 moles. Perhaps he's tying it back to the DLI of 12 hours 900µmols (39 moles)?

Have just done a search.

You're right about the DLI, he states:

For Autoflowering plants the typical light cycle is 20 hours on and 4 hours off. This maximises the time the lights are on while still allowing a few hours darkness for the plant to 'sleep' and metabolise. Because the day is longer the PAR intensity can be lower to reach the same maximum 40 DLI.

j

 

[Jaz]

Found this on the Dutch Passion site:

Many autoflower growers using long photoperiods (e.g. 20 hours per day) will err on the side of lower PPFD levels (perhaps nearer 700-800) simply to avoid pushing their plants too hard and risking light-burn problems as a result.

How much light (PPFD) do autoflower cannabis plants need?

Many growers tend to deliver slightly lower PPFD levels to autos compared to feminised strains. That’s because autoflowers grow with (typically) 20 hours of daily light, significantly longer than the 12 hours used by photoperiod strains. That in turn means that the DLI for autoflowers can get very high if long photoperiods are used in conjunction with powerful, modern LED grow lights.

For that reason, many autoflower growers using 20 hours of daily light might aim for PPFD levels of around or even below 700. Whereas they might use PPFD levels of nearer/above 1000 when blooming feminised strains. Having said that, the more experienced autoflower grower may feel comfortable pushing PPFD levels up towards 1000 near the end of bloom if the plants are thriving. However, it’s safest to do this on a case-by-case basis when the grower can use their experience to assess how that particular strain is coping with high PPFD levels in those specific circumstances.

Again, if in doubt, autoflower seed growers (especially less experienced growers) may prefer to initially lean towards lower PPFD levels of up to 700-800… only exceeding those levels when the plants are coping well and happy to be pushed harder. Growers keen to push PPFD levels as high as possible should remember the law of diminishing yield returns. Chasing maximum PPFD levels can be expensive if you are buying a high-end LED light. It may only mean modestly increased additional yields and it can come with the risk of plant problems if PPFD levels are too high for your particular strain.

However, when supplementing the grow room with CO2, higher PPFD levels can be tolerated by both feminised and autoflower strains.

A guide to grow lights PAR, PPFD, Wattage and DLI

j

 

[Delps8]

Yeah, I've seen quite a few of his vids where he's interviewing Bugbee or has Bugbee in the vid as a guest speaker.

In another vid he's at a cannabis farm, can't remember if it was with Bugbee but he's going right to the source and getting info from the right people who are successful at growing.



He's always posting about efficiency and I've even seen him include a price range, how much it would cost you to run per year, (subject to a rate per kWhr) so I guess he's looking out for the price conscious grower. You don't want to waste electricity if it's of no benefit right?



Have just done a search, here's a blog he's done:

Photos and Autos | The Recommended PAR levels for Photos and Autos

You're right about the DLI, he states:

For Autoflowering plants the typical light cycle is 20 hours on and 4 hours off. This maximises the time the lights are on while still allowing a few hours darkness for the plant to 'sleep' and metabolise. Because the day is longer the PAR intensity can be lower to reach the same maximum 40 DLI.

j

I agree - don't waste electricity if there's no benefit. That might be why he recommends those light levels but there also could be another reason. I couldn't think of the right way to put it but you stated it very well - "I guess he's looking out for the price conscious grower."

The core issue is that there is direct benefit and I've got to believe that Shane knows it. My thinking was along the lines that he can sell a less expensive product and his customers will get good results at 40 DLI. Fair enough but people who aren't aware of that these values are low won't be aware that they can significantly increase yield by adding more light.

Thanks for the link. I think I've read that and just pretty much blew is off. Reading is again, however, the light went on. This is a key point:

"If you go over the maximum I have recommended in these tables you should still get an increase in growth rate, it just may not be a '1 for 1' increase i.e. 10% more PAR intensity = 10% more growth, for example it may be 5% more growth for 10% more PAR intensity"

Note "increase in growth rate" - well, not quite. Here's what I think Shane is drawing on…

In one of Bubgee's most popular videos, he discusses how net photosynthesis (Pn) increases as PPFD increases but he points out, rightly, that the increase in Pn starts to flatten out once you hit 550µmols. Bugbee stresses that Pn continues to rise but not as quickly at higher PPFD values as it did from the 0 intercept to 500 (550) µmols.

The Chandra paper (Google for Chandra and U Miss) has similar research but add in data for different temperatures and uses a CO2 enhanced environment. Again, around 500 µmols, the slope starts to flatten.

Shane is using "growth rate" as a fair synonym for "net photosynthesis". Except it's not - and that's the rub.

The rate of increase in Pn drops of but I don't care because I'm not harvesting Pn. What Bugbee shows in his video about growing hemp is that there is a direct relationship between DLI and plant quality, crop yield, and crop quality. That's a big difference between how Pn changes and it's also an interesting one, which lead to…

A researcher, IIRC his name begins with "M" and I think the paper was published by either Guelph or someone doing ag research in Israel, who looked at that dichotomy (how can cannabis to better even though Pn is dropping?). The researcher did also find a direct relationship but, for him/them, it was a linear relationship and, second, he describe cannabis as having "plasticity", which I thought was a great way to put it. He didn't describe a mechanism that allowed that to happen but it was good to see that someone "on the business" saw that was something worth investigating.

OK, so, back to what Shane said. I understand now, thanks to you providing that link, where Shane might be coming from. That provides a possible rationale for his recommendations but that doesn't make his advice any more sound.

BTW, Shane did a recent video where he talked about designing grow lights and he said that he doesn't include far red because he's not convinced of the benefit. That's a change - until a few months ago, you could order his lights with a far red option.

 

[Delps8]

Found this on the Dutch Passion site:

Many autoflower growers using long photoperiods (e.g. 20 hours per day) will err on the side of lower PPFD levels (perhaps nearer 700-800) simply to avoid pushing their plants too hard and risking light-burn problems as a result.

How much light (PPFD) do autoflower cannabis plants need?

Many growers tend to deliver slightly lower PPFD levels to autos compared to feminised strains. That’s because autoflowers grow with (typically) 20 hours of daily light, significantly longer than the 12 hours used by photoperiod strains. That in turn means that the DLI for autoflowers can get very high if long photoperiods are used in conjunction with powerful, modern LED grow lights.

For that reason, many autoflower growers using 20 hours of daily light might aim for PPFD levels of around or even below 700. Whereas they might use PPFD levels of nearer/above 1000 when blooming feminised strains. Having said that, the more experienced autoflower grower may feel comfortable pushing PPFD levels up towards 1000 near the end of bloom if the plants are thriving. However, it’s safest to do this on a case-by-case basis when the grower can use their experience to assess how that particular strain is coping with high PPFD levels in those specific circumstances.

Again, if in doubt, autoflower seed growers (especially less experienced growers) may prefer to initially lean towards lower PPFD levels of up to 700-800… only exceeding those levels when the plants are coping well and happy to be pushed harder. Growers keen to push PPFD levels as high as possible should remember the law of diminishing yield returns. Chasing maximum PPFD levels can be expensive if you are buying a high-end LED light. It may only mean modestly increased additional yields and it can come with the risk of plant problems if PPFD levels are too high for your particular strain.

However, when supplementing the grow room with CO2, higher PPFD levels can be tolerated by both feminised and autoflower strains.

A guide to grow lights PAR, PPFD, Wattage and DLI

Interestingly enough, Shane has also worked with Dutch Passion:

j

That's very sound advice - the trick is to put that in 12 words or less.

Re. "the law of diminishing yield returns" - no citation and potential confusion with the known rolloff in the photosynthesis curve.

Re. expense - run the numbers. The only paper that I've read on that nails it right out of the gate - cannabis is such a valuable commodity that the marginal increase in cost is vastly outweighed by the increase in revenue (due to great yield and/or better quality) but electricity cost is a factor. Hence, run the numbers but one of the inputs has to be that increase in yield is linear or near linear or you'll get the wrong answer.

"worked with Dutch Passion" - he's a marketer! He sells a PAR meter and has added a couple of seedlings lights to his product mix.

 

[Jaz]

"If you go over the maximum I have recommended in these tables you should still get an increase in growth rate, it just may not be a '1 for 1' increase i.e. 10% more PAR intensity = 10% more growth, for example it may be 5% more growth for 10% more PAR intensity"

The law of diminishing returns, you'll find this just about everywhere, weight training, engine performance, the price of your speakers, TV's, etc. Pump in a 'lot' of additional money for just a slight increase in performance.

BTW, Shane did a recent video where he talked about designing grow lights and he said that he doesn't include far red because he's not convinced of the benefit. That's a change - until a few months ago, you could order his lights with a far red option.

I believe he includes red but not 'far red'.

There is some conjecture about this, yes it's not beneficial running far red for as long as the other LED's.... however, according to Emily here, you run the far red at dawn and dusk only. It's supposed to inhibit internodal stretching.

He doesn't sell a 'far red only' light so hasn't added them to his lights where they'll be on when all the other LED's are on.

j

 

[Delps8]

The law of diminishing returns, you'll find this just about everywhere, weight training, engine performance, the price of your speakers, TV's, etc. Pump in a 'lot' of additional money for just a slight increase in performance.

Speakers, yes, but headphones? Not.A.Chance. Every dollar increase $$ brings boundless improvement in audio quality!

I believe he includes red but not 'far red'.

There is some conjecture about this, yes it's not beneficial running far red for as long as the other LED's.... however, according to Emily here, you run the far red at dawn and dusk only. It's supposed to inhibit internodal stretching.

He doesn't sell a 'far red only' light so hasn't added them to his lights where they'll be on when all the other LED's are on.

j

Right - he offers the the "Full Spectrum + Red" which is the standard 660nm red but doesn't have a >700 nm option which he used to call "Pro Red".

Re. the value of "far red" - I wasn't aware of that claim. I could use some of that right now!

 

[Jaz]

Speakers, yes, but headphones? Not.A.Chance. Every dollar increase $$ brings boundless improvement in audio quality!

lol, you're clearly not spending enough on your headphones. Try the pricier end of the range, huge price increase, not that much better audio quality.

Right - he offers the the "Full Spectrum + Red" which is the standard 660nm red but doesn't have a >700 nm option which he used to call "Pro Red"

I don't think that was the case. Back in April, I ordered a light as he had a decent sale (turns out it was end of stock) and emailed him the following:

I'm very impressed with the unit and efficient delivery time. There are no labels to distinguish whether it's a Red or Pro.
How can I tell the difference by looking at it?

His response:

the PRO has 12 x red leds on each board and the +RED has 8

I had the PRO, just as I ordered, the difference: it had more LED's, (more power output) and was more efficient.

they are Samsung LM301B LEDs instead of the Seoul Semiconductor LEDs we used previously. The numbers of diodes are listed on the product pages. The new ARAY 2 is the same efficiency and PAR output as the previous PRO model

j

 

[Fenderbender]

I thought he didn't chose UV and IR leds because of questionable longevity vs the other types.
And he found any emerson effect to be very small and if you add the IR you have to balance the other side of spectrum again.

I actually just added the Aray4 at the top of my list for new led as the power and the way it's built would be excellent spread for my tent, and the price is pretty nice.
The Sanlight EVO-4 100 would also be grand but that's double the dosh.

 

[Jaz]

I thought he didn't chose UV and IR leds because of questionable longevity vs the other types.

Absolutely the case with UV, that's why he's gone with the fluorescent tubes for UV.

j