CMH vs LED vs HPS

[snakedope]

Have u ever thought why does big commerical ops put HIDs more then 3m above the plants ? What does a 3m high 1k hid ppfd look like ? Probably very lame, but still you get stellar plants and final product... How is that so ?
Even certhule would agree that light don't disappear, it's absorbed and travels until it do
So the distance is more a factor of how much light will hit your plants totally, but the plants still knows there are many high intensity sources above them, like you, you look outside and everything is nice and light is all around, your eyes are fine, but when u look up you know that the light source which create this "weak" eye level light is much more stronger then what u see here, same happens with plants, they see weak ppfd maps with HIDs but they know these weak numbers are coming from a very powerful source and react to it even though the entirety of that source don't hit em from 1 inch away.

Edit - LEDs suggest another reality, a reality of the same intensity source no matter height or other sources, this is very different from nature.

 

[JKD]

In greenhouse’s it’s for overlap + boosting ppfd in low light conditions.

 

[goingrey]

Maybe leds are more suited to specific terpene synthesis.

From the scant research i have done it seems to show led enhances lemon balm essential oil terpenes but showed a detrimental effect on menthol terpenes.

Lemon balm, that's interesting, LEDs certainly do seem to bring out the lemony aromas well.

Maybe fruity aromas in general. This is what I've noticed, that LED grown is more fruity but sunlight brings out more spicy musky incense wood resin type aromas. I suppose the latter would be more towards the menthol, or, indeed, glue.

Then we come back to the definition of quality. We can say what we want about commercial growers but I think a lot of the consumers will also look quite favorably on fruity product with higher THC content, at a potentially lower price. It might not scratch my itch quite as well but that's just me.

 

[snakedope]

In greenhouse’s it’s for overlap + boosting ppfd in low light conditions.

Sorry I meant closed greenhouse lol no sun involved
Actually I should change it to commercial indoor ops
I don't know why I called it a greenhouse
In my country they do it mostly in greenhouses with black tape that blocks the sun, not so much buildings

 

[Cerathule]

Cmon guys, ffs its not a haze comparison grow.

In my experience the 300w maxibright led lights i used never fully matured the resin glands, the terpenes were not as diverse and the resin stalks were thicker than the heads when compared to cmh.

It seems just plain wrong to think that leds don't have the required intensity to power some of these terpene biosynthesis pathways and potentially other pathways as the light seems very strong by my eyes and stronger than cfls which i've also had better results with.

Light has always many different implications. I do not believe it's the missing "intensity" or number of photons that is having a major say over what terps are being build. The number of photons mostly correlates with raw photosynthesis done, so it's about accumulation of sugars and starch, ie influencing the dry harvest mass.

It's rather the spectrum, esp. in the blue and UV region 300-500nm, maybe even up to yellow, which influences quality over stimulation via known (and maybe unknown) photoreceptors that initiate specific gene expression(s). At least, the science for this is there, or say, starting to emerge, you can grow the same genetics under white light, and in comparison under white light + supplemental narrowbandwidth UVA, and dependant on which wavelength you pick, certain terps get destroyed but others are getting increased by that. It's because the plant reacts towards the potentially harmful rays and builds substances up that "neutralizes" these before they can do damage to specific sensible proteins of the light-harvestign antenna or the electron transport chain. But that is entirely wavelength dependant and not all of these substances are actually known/researched. In the blue/green-region we may also find these as anthocyanins and others.
But then the genepool of Cannabis has grown so large, with strains having so many different terpenes to build, so it stands to reasons that even the same light recipe is working differently on various strains. And that's a huge problem for scientists because they cannot generalize what wavelengths do this or that, esp. when it's on the medicinal creation of select terps.

And then there's work by Prof. Folta that shows a still unknown novel greenlight receptor must be there, and that there may also be an unknown UVA receptor at large. Which just puts a lot of question-marks upon some of those spectrum theories...

 

[snakedope]

Excellent perspective certhule, enjoyed reading that, maybe yellow canary suggestion of putting as much more bands could be the solution ?
I only addressed the thing I saw in their numbers, I'm used to grow with high intensity lights, we all are, even cfl qualify, so that was my perspective about the difference and matter between each tech
Your perspective is making a lot of sense to me.

 

[snakedope]

But it still doesn't explain why poor hps spectra delivers killer Bud..
Are LEDs good but just built wrong ?
It seems there is a missing link here.

 

[Cerathule]

That said, HPS is really lacking the blue with only 3%, and just 1% UVA (and only if specific glass was used) and studies have shown a real benefit from upping that blue up to, say 10%, either by blue or cyan LED monochromatics or a MH. Even when the MH has less output but the blue light acts like a catalyst that makes the plants being able to utilize the HPS rays quicker.
But the problem of inequal distribution remains in all cases....

 

[Jaysways]

science is wrong and it’s all subjective. Basically is what your saying. This is like a vegan vs carnivore diet. I’m out,!such a waste of a reading time on this bollocks. @Crooked8 nice set up bruv. That’s how you do it. LEDs or not.

 

[Sativafiend1973]

@Crooked8 nice setup, you seem to grasp what LEDs are all about, this thread is falling flat and some people on here just want to be right for the sake of their ego, science is subjective and does change with new findings, we will see how this pans out on future runs for me. I still think that LEDs are top notch and the future of growing indoors.

 

[GoatCheese]

When i first tried the maxibright 300w led set up i was very impressed with the speed and size of the plants.

The plants didnt stretch as much, internodal space was reduced and the buds seemed bigger and longer.

But it never matured properly so there was no spine supporting the high causing it to quickly fade.

What i think might be an issue with Maxibright Daylight 300w – i don’t know if your light is the same model – is that they use fairly small number of led chips and push them with that amount of watts on max power. Meaning, a smaller number of chips are pushed more per chip with 300 watts than if that same amount of watts would be used to drive double or triple the amount of led chips. = individual chips run hotter (radiant heat) so their photon beams are dehydrating plant tissue more easily

...so the heat radiant side of led light beams (create hot spots) is stronger when a light fixture is built with small number of chips.

I have this problem with my diy Samsung strip lights. Led lights with smaller chip count are better suited as veg lights/supplemental lights than for blooming plants cause they will stress and dehydrate plants fairly easily when driven with more watts

 

[Wall]

to have been able to try the 3 modes of light .. without hesitation I prefer the LEDs. 15 years ago a lot of LEDs were (still) crappy But nowadays LEDs allow without problem to release 2Gr/Watt for the most productive genetics. They are very well thought out and take into account many parameters compared to HPS which remain rustic despite some efforts by manufacturers to get closer to horticultural work... (because I remember the first HPS it was REALLY public lighting , for the street, football stadiums! nothing to do with horticulture or plants!) And the CMH are nice but without comparison with current quality LEDs, then the LEDs are without danger except a little for the eyes which have hard.. bezel obliges. I could see just with 100w LEDs hyper homogeneous results and a weight of 158Gr for 100w LED only! No other lamp does such a job... and certainly not an HPS! Do you know what a 100Watts HPS is??? NO ONE WOULD HAVE THE IDEA OF MAKING GROW with 100w HPS... Logical But it may not be at all ridiculous to do it under 100w LEDs. That's a huge difference!!! There are amazing manufacturers of LEDs now and the harvests are magnificent. Just with 200w LEDS or 300w LEDs you will have a superb harvest. I think many remain in LOVE with HPS or CMH. It's their right... As some prefer to ride a bike instead of taking the Metro! Why not ! To each his own feeling... but the LEDS (even under small Watts) are REALLY Great and what a saving of money compared to HPS!!! And in the LEDs whether Cob, QB or SMD it's the same!!! In the 3 LED options the result remains SERIOUS. If people here have NEVER tried LEDs and criticize them thinking that HPS remain the Queens of Culture: GIVE A TRY! Dare to do it... familiarize yourself with LEDs. You run the risk of being very surprised (but also very happy) and you will change your tune or criticize for free something that you do not know, do not master. has never had in your grow room EVERYTHING EVOLVES! Why not you in 2023!?!?

 

[snakedope]

to have been able to try the 3 modes of light .. without hesitation I prefer the LEDs. 15 years ago a lot of LEDs were (still) crappy But nowadays LEDs allow without problem to release 2Gr/Watt for the most productive genetics. They are very well thought out and take into account many parameters compared to HPS which remain rustic despite some efforts by manufacturers to get closer to horticultural work... (because I remember the first HPS it was REALLY public lighting , for the street, football stadiums! nothing to do with horticulture or plants!) And the CMH are nice but without comparison with current quality LEDs, then the LEDs are without danger except a little for the eyes which have hard.. bezel obliges. I could see just with 100w LEDs hyper homogeneous results and a weight of 158Gr for 100w LED only! No other lamp does such a job... and certainly not an HPS! Do you know what a 100Watts HPS is??? NO ONE WOULD HAVE THE IDEA OF MAKING GROW with 100w HPS... Logical But it may not be at all ridiculous to do it under 100w LEDs. That's a huge difference!!! There are amazing manufacturers of LEDs now and the harvests are magnificent. Just with 300w LEDs or 400w LEDs you will have a superb harvest. I think many remain in LOVE with HPS or CMH. It's their right... As some prefer to ride a bike instead of taking the Metro! Why not ! To each his own feeling... but the LEDS (even under small Watts) are REALLY Great and what a saving of money compared to HPS!!! And in the LEDs whether Cob, QB or SMD it's the same!!! In the 3 LED options the result remains SERIOUS. If people here have NEVER tried LEDs and criticize them thinking that HPS remain the Queens of Culture: GIVE A TRY! Dare to do it... familiarize yourself with LEDs. You run the risk of being very surprised (but also very happy) and you will change your tune or criticize for free something that you do not know, do not master. has never had in your grow room EVERYTHING EVOLVES! Why not you in 2023!?!?

Another weight guy ? Shishh..
Valuable opinion nonetheless.

 

[GoatCheese]

Take into account my friends, that all LED lights are not built the same and don't have the same number of chips per the same amount of output!
The lights with larger number of chips on them aren't stressing plants as much as the lights with fewer chips on them = less radiant heat hitting plant tissue which will cause dehydration (..and evaporation of some of the compounds in the resin along with the moisture?)

 

[Cerathule]

But it still doesn't explain why poor hps spectra delivers killer Bud..
Are LEDs good but just built wrong ?
It seems there is a missing link here.

You need to start formulating reasonable, precise and non-naive questions.... otherwise what discussion do you expect to initiate?

 

[Jaysways]

@Crooked8 nice setup, you seem to grasp what LEDs are all about, this thread is falling flat and some people on here just want to be right for the sake of their ego, science is subjective and does change with new findings, we will see how this pans out on future runs for me. I still think that LEDs are top notch and the future of growing indoors.

They have to be the future…

 

[chilliwilli]

No, intensity is measured at source, not in space
You can't measure intensity in ppfd as it's source related not space related !

Thats not true

https://en.m.wikipedia.org/

 

[greencalyx]

But it still doesn't explain why poor hps spectra delivers killer Bud..
Are LEDs good but just built wrong ?
It seems there is a missing link here.

I would like to see a definitive experiment done where someone builds an led light that mimicks exactly an hps, and just change one variable at a time.

As far as I can tell, the only differences between hps and led are, spectrum, heat output, and diffusion.

By diffusion, I mean how with hps, the photons emitted by the bulb bounce around the reflector and get scattered and leave the fixture at many different angles. As opposed to leds which are a bit more focused. I personally think that diffusion is what gives better "canopy penetration."

I use quotes because I don't think it is about having a light source so powerful it actually penetrates the leaves/canopy. It is more about the photons being able to go around the leaves/canopy instead. And that is much easier when you have your light coming out of your fixture at all sorts of different angles like with hps.

Diffusion would be the hardest variable to measure/quantify, But probably can be done

 

[bigtacofarmer]

It would be interesting to get a spectrometer and grow out a bunch of strains under a variety of lights. And do all the testing and data collecting. Then do a bunch of blind taste tests. And see what is learned.

 

[YellowCanaryConsulting]

@Crooked8 I still think that LEDs are top notch and the future of growing indoors.

Yes and future leds will look like this:

Veg:

Bloom;

You take the dreaded blurple and divide it into blue heavy channel and red heavy channel. Like they should have always been. Switches are too complicated tho so you'll have to buy two separate lights until led toggle switch technology catches up.

But it still doesn't explain why poor hps spectra delivers killer Bud..
Are LEDs good but just built wrong ?
It seems there is a missing link here.

Of course they are built wrong. The scene/industry spent decades promoting the concept of dedicated 27-2100K bloom and 4-10000K veg,only to turn around and sell everyone 3000K dual (neither) purpose crap. I don't know any kid who picked up an old high times and doesn't know blue for veg (roots), red for bloom (buds). This is the type of fraud that runs the world, hoping everyone forgets the obvious truth so they can sell more half assed crap.

If you look at the spectral peaks of the various cryptochromes, phytochromes, phototropins, zeitlupe, UVR8, chlorophylls, xanthophylls etc, you'll see none of these common led light manufactures are even trying to hit those peaks. The idea seems to be, we don't need phytochrome B D or E because we gave them phytochrome A, they should be happy with that until next year when we stick a 830nm chip on the board and call it the ZX model.