[PetFlora]

The old school MH/HID/HPS crowd shouts from the rafters that LEDs do not compare, yield-wise. Well, among the problems:

1. Most grow books were written pre-LED, their grow data is based on these energy sucking, low PAR, dinosaurs.

What we need is new data:

PPDF relates to photon flux density, like PAR (photosynthetic active radiation) or USABLE PHOTONS.

The HPS and MH crowd may not be aware that their lights are averaging 37% PAR, at best, while cool operating LEDs are 100% usable light.

My current journal has morphed into 950 watts CFL vs 90 WATTS LED, with 50 watts of softwhite CFL on one side, below the canopy. It seems our girls benefit from some underside lighting as well

As you can imagine, the CFL side has more buds, and bigger buds, but not 9 times more- maybe 2 times more. In the end the yield wasn't dramatically different between the two sides, but the test morphed along the way due to a blown transformer in the LED

Based on 2 grows under a UFO 90, I think a 200 watt LED is a good entry point for 3-5 plants that have a substantial canopy, and grow in the 3 ft range, or 4 lowryder types that grow like colas, with minimal side branching. But again, I think under canopy light should not be neglected.

[groady-ho]

maybe they are misunderstood, maybe not..until the price comes down and they yield what my 1k hps does they make no sense to me..
cost vs. yield vs. savings = led is not good buy..for the time being..
i'm sure as they evolve, they might be the future..

Originally Posted by PetFlora

The old school MH/HID/HPS crowd shouts from the rafters that LEDs do not compare, yield-wise. Well, among the problems:

It's not about yield, it's about irradiance, and that we want high irradiance for highest rates of Pn (rate of photosynthesis) which happen to also allow for highest yield (as long as other grow variables are in order like Vapor Pressure Deficit, fertilizers, temp, Co2, etc). That is why using yield to compare lamps (either LED or HID) is wrong, there are too many variables effecting yield to use it as a quantifier.

1. Most grow books were written pre-LED, their grow data is based on these energy sucking, low PAR, dinosours.

PAR is merely the range of 400-700nm, it IS NOT irradiance! And in terms of PAR range HID offer the full range, where GREEN is very important, yet LED arrays are very weak on green, if they offer any green at all! We want and need the whole PAR range, LED arrays focus on red and blue and that is dumb; blue has the lowest QY (Quantum Yield) of all three, that is, blue offers the lowest Pn.

What we need is new data:

PPDF relates to photon flux density, like PAR(photosynthetic active radiation) or USABLE PHOTONS.

What we NEED is for LED users and LED makers/seller to actually understand the quantum physics of lights, which they do not at present.

PPDF is not a qualification, however, PPFD is. PPFD = Photosynthetic Photon Flux Density.

PAR is NOT irradiance, the use of the term "PAR watts" is totally inaccurate and wrong; SunMaster is bunch of idiots for using it. LEDGirl, et al, love to state their arrays offer high PAR watts (i.e., watt/m^2), but the problem is that is measured at the source (i.e., the lamp); AND plants don't use watts, they use photons.

The HPS and MH crowd may not be aware that their lights are averaging 37% PAR, at best, while cool operating LEDs are 100% usable light.

That is not a correct statement in terms of what makes plants grow, we need to know the irradiance, not the radiant energy. It matters not how much watts from HID are converted into PAR range photons, what matters is the amount of PAR range photons reaching the plant, i.e., PPFD. And LED arrays can not emit enough PPFD to reach peak Pn as they are commonly hung from canopy, or even close to it! (but neiter can a 250w or 400w HID for the matter) That is why 600w to 1,000w HID is best, and not any HID, i.e., a 250w HID is just silly. We need high irradiance HID of 600w or greater, preferable 1,000w to grow the best cannabis in terms of Pn (and Pn controls basically all other variables).

So what that a LED array emits light only in PAR range? The important point is how many/often photons within PAR range reach the canopy per sq meter per second, ala PPFD.

Also, not all photons are created equal. Blue photons offer the lowest Pn, while green photons offer the highest Pn with red photons offering the 2nd highest Pn. And guess what? LED makers love to cite the chlorophyll A/B absorption spectra which show absorption peaks in blue and red, however, that is NOT a real expression of how plants work. That chlorophyll A/B absorption spectrum is made from in vivo aqueous extract of leaf in a spectrophotometer, which is why those graph ARE NOT VALID!!! And as such, all the claims made by LED sellers like LEDGirl and LED users like you go up in a puff of smoke...they are not valid in any sense of the word. We need to use an updated version of K.McCree's QFD (Quantum Flux Density), i.e., QY (Quantum Yield) curve which shows how plants REALLY use photons within PAR range, please see the links in my sig for much more CORRECT info. And please read my posts in that whole thread; the claims made by LEDGirl are lies, even though she may not realize it because she has no grasp of light quantum physics.

My current journal has morphed into 950 watts CFL vs. 90 WATTS LED, with 50 watts of softwhite CFL on one side, below the canopy.

What a waste of time! Why not use HID????

As you can imagine, the CFL side has more buds, and bigger buds, but not 9 times more- maybe 2 times more.

And what does that show? Nothing, that's what it shows. Yield as I already wrote is a VERY poor way to compare lamps.

Based on 2 grows under a UFO 90, I think a 200 watt LED is a good entry point for 3-5 plants that have a substantial canopy, and grow in the 3 ft range, or 4 lowryder types that grow like colas, with minimal side branching.

I assume you are basing your opinion on yield? Sigh....


I for one would never flower with less than a 600w HID, why risk getting arrested (in many states/countries) for a low yield from low irradiance?

[globel]

LED's are over priced and do not perform as well in "real life" as they do on paper.

I donno how they go about charging 500+$$ for something made with 30 50cent led's

Not to mention have you ever seen bud grown under led. Yuk.... usualy very harsh jam packed with leaf instead of cylax

yea I agree, even a member called VerdantGreen loves to brag about his leafy buds and post pics too...hehe, silly VG!.

[globel]

If you think using yield to compare LED to HID is wrong, then your bat nuts crazy. Yield is the ONLY thing that matters when talking about growing. Yield is the only thing that matters when talking about grow lights.


If you follow my logic. A healthy plant will on average yield more then an unhealthy plant. And if a plant yields more with an HPS compared to a LED. Then the plants grown under the HPS are healthier.



LEDs going to be skipped for plasma lights just like HDDVD did for bluray

[PetFlora]

Very good input here. Let's keep it going with meaningful info.

It occurs to me that bulb replacement, which will be an issue down the road, might turn the tide away from LEDs, at least as we currently know them. G2leds are all white, but I have no idea whether they are 1 watt or what.

Secondtry- I noticed your sig over several threads says you are taking a break, but still you repsond, so maybe that is an old statement.

globel. I am 3/4 the way through my second LED grow. My buds look fine. Lots of calyx. One of my friends (an old hippie) says he has never smoked anything as smooth

[asde²]

Originally Posted by PetFlora

The HPS and MH crowd may not be aware that their lights are averaging 37% PAR, at best, while cool operating LEDs are 100% usable light.

hid light output is most likely 100% in par range. the basic efficiency of an 600w hps is ~37%. led base efficiency max on market ive seen is ~44% (a cool white) - 100% base efficiency is not possible.
base efficiency for leds used by growlight builders is a secret aka no seller publish those information but its most likely less than 25%.
its already possible to build a 600w led light which can keep up with or even beat (not by 400% or close to it..) a 600w hps but it would be very expensive (2000$+).

Originally Posted by globel

If you think using yield to compare LED to HID is wrong, then your bat nuts crazy. Yield is the ONLY thing that matters when talking about growing. Yield is the only thing that matters when talking about grow lights.

Originally Posted by globel

If you follow my logic. A healthy plant will on average yield more then an unhealthy plant. And if a plant yields more with an HPS compared to a LED. Then the plants grown under the HPS are healthier.



LEDs going to be skipped for plasma lights just like HDDVD did for bluray

I dare and challenge ANY LED lover to prove me wrong with data, not their silly yield info which has as much to do with growing environ and skill of grower as it does the light.

Don't even get me started on the plasma light BS. It has WAY too much blue photons which offer the lowest Pn and will heat up the leaf thus lowering VPD and intern lowering Pn even more! This all equates to lower yield. Do a search for "plasma" and my name for what I have written about many times before...if blue photons are not used for photosynthesis they are turned into HEAT at the leaf.

None of you guys/gals seem to understand the FACTS of light quantum physics, especially in regard to plants!

I have ALREADY shown countless times what we need in terms of irradaince for peak Pn, and LED arrays as they are commonly hung DO NOT EMIT ENOUGH PPFD TO REACH PEAK Pn IN CANNABIS, PERIOD!!! (and neither do 250w, 400w and most 600w HIDs for that matter)