Comparing lights: pinning down reliable parameters

[Lowrider72]

Yeah, I dont just mean CMH...all full spectrum lights LED included.
I see LED panels make some pretty high uMol figures, but what spectrum do they cover?
I think its somehow a balance of uMol output, spectrum coverage, decent CRI index %....and where these uMol outputs occur at stages in the output spectrum.

If there is some formula between those Im sure a base line could be found.

 

[LiberalThinker]

I've spoken to quite a few guys that grow solely with those 315cmh, the cool looking ones with the big solid hood. Every one of them swear it makes stronger buds than HPS.
I don't know much about lighting (obviously or I wouldn't still be using those blurples lol) but maybe one of you guys would know if there's a logic behind that relating to the spectrum?

Have a look at this graph of some light sources I've annotated:

The dotted McCree Curve is what the plant can use and how much. The most faded graph at the back is the natural sunlight range. The slightly less faded is HPS, then Blurple out front. Ideally, we want a light to fill all the space under the McCree curve . CMH is missing there. As you can see, only sunlight is anywhere near doing that. If you look at the CMH graph again from earlier post above, you can see it does a pretty good job of filling in that space:

I don't know the best LEDs but this is a Spectrum King 600, which doesn't do a bad job either:

It should be noted that the McCree Curve does not account for Far IR and UV which have, since it was conceived, been found out to have photosynthetic effects. Blurples work ok because their frequencies are concentrated around the peaks of the McCree Curve where the plants response is highest.

 

[Lowrider72]

Thats some excellent work there Yellowbelly. Thats the sort of spectrum comparison needed.
Great info.... 5 stars!

 

[Old Salt]

I went through this anguish when I bought my 'blurple,' and when I designed my DIY light. There are many photosynthetic response curves out there. I used this one:

Photosynthesis Spectrum​

I even found one in these forums for cannabis:

Cannabis Photosynthesis Spectrum​

I quickly found out that not all 'blurples' are created equal. I came to this conclusion by superimposing the photosynthesis spectrum over the spectrum of various fixtures. Here's the result for the 'blurple' I ended up purchasing:

'Blurple' Spectrum with Superimposed Photosynthesis Spectrum​

I'll pull out the 'blurple' spectrum for discussion:

'Blurple' Spectrum​

From this data I consider the luminous efficiency, and Lumen output of the fixture and to be the most important parameters. This fixture produces 24661.9 lumens with an luminous efficiency of 75.12 LM/W. Note that this is not the luminous efficiency of the emitters, just the fixture as a whole including the drivers, and fans. I opened the fixture and found the fans use 5W each, and the drivers were 85% efficient. A calculation shows that the emitter luminous efficiency is 24661.9LM / (0.85 X (328.3W - 3 X 5W)) or 92.6 LM/W. This is the figure that should be used to compare a solid state emitter to a HID emitter (bulb). The value of 75.12 LM/W is used when you compare a solid state fixture to the luminous efficiency of the HID prorated for the efficiency of the ballast, and power for extra cooling of the bulb.

 

[TorturedSoul]

The importance of CRI has been overrated in the industry, IMHO (remember, those initials stand for In My Honest Opinion, lol).

Those charts with the curvy lines on top are awesome. But if you put them all together on a graph and make a curvy line that covers all of them... There's not a lighting product on the market that produces that spectral curve. Okay, fine, pick something as close as you can get.

But that's problematic, yeah? Because these two companies' products are closest to it in this part of the spectrum, and that company's products are closest to it in this other part of the spectrum, and a fourth company kind of matches it, mostly, but the output looks a little low which wouldn't even be noticeable on a graph except for the big spike here and up there, et cetera.

If it's just "the more, the better," fine here, too, because you could just keep adding different lights until you've blasted every portion of the spectrum that even might be useful to the plant.

Only, wait, what's this? Certain portions of the spectrum can cause certain behaviors/processes, certain other portions of the spectrum can retard certain behaviors/processes, and I'm just a guy who wants to grow a bit of bud now and then who cannot afford a building the size of Boeing's Everett factory (4,280,000 sq ft, lol) and the budget to fill it with different setups in order to experiment. Nor do I possess 3,000 clones (each) of several different strains (to allow for the possibility that genetics that evolved in different locations on the planet might respond somewhat differently to any given light spectrum) so that there'd be some hope of actually getting useful results from my experimentation.

Which means that when I read something or other a while back about how hitting plants with different ratios could change their behaviors... I started feeling a little concerned. Seems like it was something having to do with using strong red (far-red? near-red? IDFK...) light at the beginning of the day. Or the end of the day. Or maybe just after the day ended, after having used some other supplemental frequency light for a time immediately before lights-out.

Or... something.

So I'm thinking, "More light = more plant." But I'm also thinking "change the ratio of the lighting, change the growth pattern, length of flowering period, length of stretch period, amount of stretch, cannabinoid content, terpine content (for both of those, maybe just amounts, maybe the ratios of them), maybe all kinds of things, even incidence of opposite-sex flowers."

Or not. But if I was shopping for lights right now, I'd be pretty <BLEEPing> stressed out before I was finished. Things were easier pre-Internet, lol - you just went to the local (or nearest, which might be a three-hour drive) store and went in to find out what they felt like selling you that day, then bought whatever your budget would allow.

 

[Old Salt]

if I was shopping for lights right now, I'd be pretty <BLEEPing> stressed out before I was finished.

Exactly! That's what I went through a few years ago, and partly why I built my own light. I see the same thing with new members wanting to start their first grow.

My other pet peeve is that most of the lights sold are physically too small for the purpose. The manufacturers recommend that they are placed 2' or more above the canopy. This means you lose 2-1/2' of your height to lighting. Toss in a filter to get rid of another eight inches, allow a foot for your containers, and a 5' tent has only 10" of room for the above ground part of your plants. Spreading the emitters further apart, or using more light fixtures will allow you to get as close as 6" to the canopy making the above ground grow height 28". For the compact LED fixtures you want a minimum of a 6' tall tent, preferably taller. This is one of the factors that led to the rapid acceptance of the Quantum boards, and why many like the Timber Grow Lights. You get a more even light coverage in your tent.

 

[LiberalThinker]

The importance of CRI has been overrated in the industry, IMHO (remember, those initials stand for In My Honest Opinion, lol).

Those charts with the curvy lines on top are awesome. But if you put them all together on a graph and make a curvy line that covers all of them... There's not a lighting product on the market that produces that spectral curve. Okay, fine, pick something as close as you can get.

But that's problematic, yeah? Because these two companies' products are closest to it in this part of the spectrum, and that company's products are closest to it in this other part of the spectrum, and a fourth company kind of matches it, mostly, but the output looks a little low which wouldn't even be noticeable on a graph except for the big spike here and up there, et cetera.

If it's just "the more, the better," fine here, too, because you could just keep adding different lights until you've blasted every portion of the spectrum that even might be useful to the plant.

Only, wait, what's this? Certain portions of the spectrum can cause certain behaviors/processes, certain other portions of the spectrum can retard certain behaviors/processes, and I'm just a guy who wants to grow a bit of bud now and then who cannot afford a building the size of Boeing's Everett factory (4,280,000 sq ft, lol) and the budget to fill it with different setups in order to experiment. Nor do I possess 3,000 clones (each) of several different strains (to allow for the possibility that genetics that evolved in different locations on the planet might respond somewhat differently to any given light spectrum) so that there'd be some hope of actually getting useful results from my experimentation.

Which means that when I read something or other a while back about how hitting plants with different ratios could change their behaviors... I started feeling a little concerned. Seems like it was something having to do with using strong red (far-red? near-red? IDFK...) light at the beginning of the day. Or the end of the day. Or maybe just after the day ended, after having used some other supplemental frequency light for a time immediately before lights-out.

Or... something.

So I'm thinking, "More light = more plant." But I'm also thinking "change the ratio of the lighting, change the growth pattern, length of flowering period, length of stretch period, amount of stretch, cannabinoid content, terpine content (for both of those, maybe just amounts, maybe the ratios of them), maybe all kinds of things, even incidence of opposite-sex flowers."

Or not. But if I was shopping for lights right now, I'd be pretty <BLEEPing> stressed out before I was finished. Things were easier pre-Internet, lol - you just went to the local (or nearest, which might be a three-hour drive) store and went in to find out what they felt like selling you that day, then bought whatever your budget would allow.

Science is always a work-in-progress. I like science. What we are discussing is the current state of the art. We'll never know everything about it but we can know more than we did before... It's all relative and, to me, it's worth exploring... just for the experience of seeing how futile it is. .

 

[SOG001]

I love my vero 29's I run 12 of them over a 4' x 5' x 8; grow area and harvest a pound per plant. if I boost the drivers from 1400mA to 2100mA that would mean an increase in yield ?

 

[Old Salt]

You should, but check the light intensity now. If you are over about 65000 Lux at the canopy, you won't get much more without CO2.

 

[TorturedSoul]

I love my vero 29's I run 12 of them over a 4' x 5' x 8; grow area and harvest a pound per plant.

How many plants, and what's the (average) grams per square foot and (average) grams per watt in those 20 square feet?

 

[Mayne]

Yeah, I imagine it's a big deal in some countries. Here in Blighty we don't see above 25C often. I could quite happily grow all the time on this Phillips Sodium Green Power 600w but I imagine the CMH is better. Shall find out soon. This is my plant under the Philips dimmed to 250w. I've photographed it under T5's for better colour:

over feeding

 

[Mayne]

The importance of CRI has been overrated in the industry, IMHO (remember, those initials stand for In My Honest Opinion, lol).

Those charts with the curvy lines on top are awesome. But if you put them all together on a graph and make a curvy line that covers all of them... There's not a lighting product on the market that produces that spectral curve. Okay, fine, pick something as close as you can get.

But that's problematic, yeah? Because these two companies' products are closest to it in this part of the spectrum, and that company's products are closest to it in this other part of the spectrum, and a fourth company kind of matches it, mostly, but the output looks a little low which wouldn't even be noticeable on a graph except for the big spike here and up there, et cetera.

If it's just "the more, the better," fine here, too, because you could just keep adding different lights until you've blasted every portion of the spectrum that even might be useful to the plant.

Only, wait, what's this? Certain portions of the spectrum can cause certain behaviors/processes, certain other portions of the spectrum can retard certain behaviors/processes, and I'm just a guy who wants to grow a bit of bud now and then who cannot afford a building the size of Boeing's Everett factory (4,280,000 sq ft, lol) and the budget to fill it with different setups in order to experiment. Nor do I possess 3,000 clones (each) of several different strains (to allow for the possibility that genetics that evolved in different locations on the planet might respond somewhat differently to any given light spectrum) so that there'd be some hope of actually getting useful results from my experimentation.

Which means that when I read something or other a while back about how hitting plants with different ratios could change their behaviors... I started feeling a little concerned. Seems like it was something having to do with using strong red (far-red? near-red? IDFK...) light at the beginning of the day. Or the end of the day. Or maybe just after the day ended, after having used some other supplemental frequency light for a time immediately before lights-out.

Or... something.

So I'm thinking, "More light = more plant." But I'm also thinking "change the ratio of the lighting, change the growth pattern, length of flowering period, length of stretch period, amount of stretch, cannabinoid content, terpine content (for both of those, maybe just amounts, maybe the ratios of them), maybe all kinds of things, even incidence of opposite-sex flowers."

Or not. But if I was shopping for lights right now, I'd be pretty <BLEEPing> stressed out before I was finished. Things were easier pre-Internet, lol - you just went to the local (or nearest, which might be a three-hour drive) store and went in to find out what they felt like selling you that day, then bought whatever your budget would allow.

The problem isnt the spectrum, the problem is people use ALL THE LIGHT, ALL THE TIME, thinking, more light-more yeild. And thats just not true.

The best all around , is 4100K, if you want to get even better, then a mix of 3000K and 4500K, and you want even better you say? 660-680NM and 710-730 NM to hit Emerson, of course, adding CO2 to any grow, will boost any grow, because CO2 is a main link in the growth.

More Light=More yeild happens after the 4th week of Flower, after the final stretch phase, THEN hammer them with photons, because thats the building phase. Mag is a MUST, And finish with 6500K if you want mega frost last week before chop.

BUT, if your over feeding, over watering, and blasting them with photons early in their life, they feel the pain thru the entire grow.

 

[TorturedSoul]

adding CO2 to any grow, will boost any grow, because CO2 is a main link in the growth.

Even one that is insufficiently illuminated and in which the temperatures never rise above 74°F, lol? I suspect that the average ambient level of CO₂ (which I think was determined to be something like 405 PPM in 2017, which would be higher than it's been for... IDK... 800,000 years or more) would be more than the plant would be likely to use under those conditions - so you might want to add a couple qualifiers to your statement.

CO₂ is necessary. But there's a relationship between that, temperature, and amount of light-energy that the plant is receiving. Which you are probably well aware of, I assume. I'm just pointing out the obvious because it may not be so obvious to everyone who will read this thread.

More Light=More yeild happens after the 4th week of Flower, after the final stretch phase, THEN hammer them with photons, because thats the building phase. Mag is a MUST, And finish with 6500K if you want mega frost last week before chop.

BUT, if your over feeding, over watering, and blasting them with photons early in their life, they feel the pain thru the entire grow.

I'll agree that it's not necessary (and not always even helpful) to supply as much light-energy during the growth phase as in the flowering one - at least if the gardener is using the same space for everything, because it could lead to overcrowding later on. But I cannot say that it's harmful over and above that. Plants grown outdoors at the equator receive pretty much the same amount of light from seed to harvest. And equatorial landrace sativas grown in their natural environment are not known for being small plants .

I do agree - and with NO reservations this time - about the other two things you mentioned, though. Overfeeding and watering too much/often... The latter especially can be a problem that newbies have trouble with, because too much and too little water can each make a plant "lie down," so to speak.

Again, I'm not trying to be an @ss with the nitpicking. It's just that some of the things we take for granted... Well, we routinely see new members who've never grown a cannabis plant before (or, perhaps, not any kind of plant). Things that are obvious probably aren't obvious... to them. If my buddy called and asked me a question having to do with electrical wiring, circuits, load-balancing, how the length of the wire run affects resistance, etc., I'll make some assumptions when answering him because I know that he has at least a gross familiarity with the concepts and some practical experience. If my 78-year old mother, on the other hand, asked me the same question, I'd have a completely different answer because I'd know that she lacked both of those things. Er... Like that, only with cannabis .

 

[Mayne]

absolutely man, Higher temp, higher Light intensity, higher CO2 usage, or efficiency.