Investing in new lights LED or HID?

[Zombo]

Hey Zombo,

......

That's great. However, I have not tried to imply, nor have I written LEDs like the kind LEDGirl sells do not grow cannabis. My problem is the claims made by LEDGirl and other LED sellers, i.e. comparing them to HID using lux to PPFD, etc, and no one testing lamps themselves. I state HID lamps with good SPD used correctly (ie., PPFD) is better for cannabis than LED considering the technology of LED panels today and I assume as it will be for many years to come. If growing in a space where heat or height is a problem LED can be a solution for sure, but LEDs won't grow cannabis like HID will grow cannabis (in terms of PPFD).

......

FWIW: I am going to use "PPFDi" with quantum sensor when measuring light/plant interaction. PPFDi is PPFD of the canopy, intracanopy and bottom of canopy; thus it's much more representative than just PPFD at top of canopy.


HTH

So to apply Occam's Razor to this all:

You believe the PPFD data posted on LEDGirl's site to be erroneous, based on a calculation using the lux values measured -- as opposed to actually measuring the PAR/PPFD with an instrument designed for that measurement specifically?

PPFDi of the canopy? The canopy of what? Are you planning on me volunteering my unit for you to do a grow?

Would you be willing, should I provide you a 126w unit by one means or another, do a comparison grow of your own, and utilize your meters to collect raw data? Then will you produce a comprehensive and peer-reviewed paper?

Believe me, I'm trying to not be antagonistic, rather I would enjoy the production and presentation of a side by side scientifically controlled grow with all aspects of data collection available, including RH, temperatures, the irradiance of the units at given levels in vivo/situ (pick one) and most importantly to the members of these forums, a comprehensive evaluation of the buds, volume, density and trichome density.

 

[mad librettist]

now that would be cool!

 

[secondtry]

Hey Zombo,

So to apply Occam's Razor to this all:

You believe the PPFD data posted on LEDGirl's site to be erroneous, based on a calculation using the lux values measured -- as opposed to actually measuring the PAR/PPFD with an instrument designed for that measurement specifically?

Yes, but it's not only her site, SunMaster is also guilty of similar trespasses (i.e. not reporting PPFD), as are all other LED sellers websites I have seen. Someone in this thread asked about plasma LED panels and that site uses the same method as LEDGirl to find PPFD (I assume).

We know for cannabis to reach peak rate of photosynthesis, growth and yield we want a PPFD of ideally 1,500, but 1,300-1,500 seems fine.

I too have used the suggested methods to find PPFD from lux, etc, but it's not an accurate conversion, apples to oranges. My problem is LED sellers represent it as an accurate conversion, and to me LEDGirl's PPFD page seems to imply 500-700 PPFD is ideal for cannabis, however, I have shown that is not the case, we need at least double that irradiance.

I also don't like how LED sellers make claims about watt vs watt, etc, i.e. comparing a 300w LED to a 400 w HID is not valid. A valid comparison would be PPFD emitted at X distance. And stating an HID emits 60% unusable light is a lie, plants use green light very well, in fact they use all light in the PAR range for photosynthesis contrary to what LED makers so often claim. The problem is they use the chlorophyll A and B absorption spectrums, but they are not valid, we need to use PAS (Photosynthetic Action Spectra). Thus HID do not emit only 40% light a plant can use, and HID emit more wavelengths with high rates of photosynthesis (ie., red and green) than LED panels.

PPFDi of the canopy? The canopy of what? Are you planning on me volunteering my unit for you to do a grow?

I only mention PPFDi as a matter of interest to measuring the light available to plants to better understand light distribution in the grow. If PPFD is 2-D (the surface of the canopy) then PPFDi would be 3-D (the PPFD from the "whole canopy") which allows for more efficient light usage and much more accurate trimming of fan leafs, LST, plant placement, etc (all to increase/better use PPFDi). It does not have much to do with LED vs HID; I just thought people would be intersted to read about it.

Would you be willing, should I provide you a 126w unit by one means or another, do a comparison grow of your own, and utilize your meters to collect raw data? Then will you produce a comprehensive and peer-reviewed paper?

No, that's not my plan. I don't see a need to do a grow, but thanks for the cool offer. What I am going to do is find PPFD of LED panel at X, Y and Z distances and also at what distance the LED panel must be placed to emit 1,500 PPFD (I don't think they will emit that much irradiance except maybe a few inches away from canopy, or closer). Then I will make nice graphs and such and report the data.

I plan to do the same testing with my Sun System II reflector, Nextgen digital ballast and 600w Hortilux Super HPS. After that I plan to test a 400w Sun System II, Hortilux Blue lamp and Nextgen ballast and then I plan to test a 1,000w PL reflector with Nextgen digital ballast and Hortlilux Blue lamp. After that I will test a LEDGirl LED panel (big, new kind). And then I will test many different 400w, 600w and 1,000w lamps. From there I will move on to testing as many reflectors as I can talk dealers out of (I will use my data from lamps as an example of why they should trust me). Next I will test different ballasts and combos, etc. I want to test the SunPluse lamps first because I don't like how they report lamps by Kelvin, then I will test SunMaster because I don't like how they report lamps by PPF (which they mis-term of PAR watts).

Zombo wrote:

Believe me, I'm trying to not be antagonistic, rather I would enjoy the production and presentation of a side by side scientifically controlled grow with all aspects of data collection available, including RH, temperatures, the irradiance of the units at given levels in vivo/situ (pick one) and most importantly to the members of these forums, a comprehensive evaluation of the buds, volume, density and trichome density.

I don't think your being antagonistic at all, questions are good. I will do a side by side using scientific method and all the qualifications you mention plus a few more with one of LEDGirls big panel vs. Horlitlux blue 1,000 both at 1,500 PPFD if the LED panel can reach 1,500 PPFD. Then I would be interested to see a side by side and I would indeed write a paper on it, even with pics

I could be setting myself up for the biggest foot-in-mouth ever, but I don't think so. I am willing to accept I could be, and when I test I of course won't skew any data, I could never do that I value data to highly to disrespect it like that.

I vote for in vivo. But I see your point.

Thanks.

 

[outdoe]

I looked at those myself, but at $475 the 400w HPS setup with a digital ballast and exhaust fan was cheaper at this site http://www.htgsupply.com/ If the 126w Penetrator was 75 to 100 dollars cheaper I would probably try it. If I am going to invest in something new and possibly not as efficient, there has to be some sort of price incentive, but that is just my opinion. I have seen several posts that show the 126w penetrator in action and it looks like it does well, but I have yet to see the massive colas I see in HID grow rooms. So for now I will be going with an 400w HPS.

But a couple other nice things to consider with LED lights are the life span and energy savings. You get about 24,000 hours out of a 400w HPS bulb which is just under 3 years on contsant 24/7 use. With the LED you get 100,000 hours average life span and that is well over 10 years of constant 24/7 use add to it the energy savings of no ballast and nearly 1/4 the kilowatt hours and it is a very cost effective buy in the long run. However I need immediate cost savings not long run so its better for me to go with what I know and that is HPS gets results.

only concerns of that is that Lotta people dont use a Bulb more then a year let alone 3. I switch every grow Because the bulb degrades. Lumens are lost. LED will degrade as well. I dont know how often they would need to be replaced for maximum results but it will come at a cost higher then a bulb. 10 years of using the same LEDS will be like watching your crop get smaller and smaller

 

[mad librettist]

Aw, come on 2ndtry, can we just get a bit empirical and do a grow? It can be stealth with an LED, no?

Tell me, is there anything to the idea of light penetration? I think that's what he's getting at with the proposed test.

 

[Zombo]

Aw, come on 2ndtry, can we just get a bit empirical and do a grow? It can be stealth with an LED, no?

Tell me, is there anything to the idea of light penetration? I think that's what he's getting at with the proposed test.

Exactly.

 

[secondtry]

Midday Depression and multi-peaks of diurnal (daily) net rate of photosynthesis (Pnnet):​

Many outdoor and greenhouse plants experience what is known as "midday depression": when Pn (rate of photosynthesis) drops around midday. If the Pn does not increase later in the day the daily Pn flux is a one-peak graph. If after midday depression the Pn increases (ex. due to decreased VPD (Vapor Pressure Deficit) in the evening) the daily flux of Pn is a multi-peak graph, usually having two peaks. When growing plants inside we are still concerned about midday depression and multi-peak Pn, however, we have great control over the environment, and thus over the occurrence of midday depression and multi-peak daily Pn. If we strive to prevent midday depression the daily Pn flux will be a one-peak and flat rate after that (once "steady-state photosynthesis" is reached).


The reason we want to prevent midday depression is the higher the Pn the greater potential growth, healthy, quality and yield of cannabis. It seems surprising easy to prevent midday depression.


Below I will list what is thought to cause midday depression of Pn:



Main Physiological Cause:

• Decrease in leaf stomatal conductance, usually by closure of stomata.

Main Biochemical Cause:

• Decrease in activated rubisco (RuBP)

• Decrease in PS II QE (Photosystem II Quantum Efficiency), e.g., when a leaf uses photons within PAR range less efficiently to drive photosynthesis, often caused by light saturation and resulting photoinhibition.

Main Environmental Causes:

• VPD = when VPD is too high the stomata close decreasing stomatal conductance.

• Soil-Water Status = when the media is dryish [sic] (i.e. low plant "available water") the indirect result is decreased stomatal conductance thought to be from an increase in ABA (Abscisic Acid).

• Light Saturation = too much PPFD is not good; do not exceed 1,500 PPFD for cannabis to be safe (this should not be a concern for growers who use less than 1,000watt HID)

• Activated Rubsico (RuBP) = a decrease in active RuBP limits Pn and Pnmax because activated RuBP is a limiting factor of photosynthesis. The main chemical that activates RuBP is RuBP "activase". If RuBP activase decreases there is a resulting limit to activated RuBP because RuBP activase is what turns inactive RuBP into active RuBP. Total RuBP is not thought to cause midday depression, only the level of activated RuBP is thought to be the culprit. It then follows that we want to limit the decrease of RuBP activase and lucky for us that is a trivial task. RuBP activase is decreased under two conditions: 1) high heat, over 89'F is bad; and 2) high Co2, I have found studies showing over 1,200 ppm can reduce RuBP activase and that matches Co2 saturation levels for cannabis (which maxes out at about 1,000 ppm of Co2). Thus to prevent a decrease in activated RuBP we should keep temperature under 89'F and keep Co2 levels below 1,200 ppm (I use 1,000 ppm).

Environmental Factors That Are Not Causes:

• Daily Light Integral = the total irradiance per day is not a cause of midday depression, however, PPFD is a cause in the form of photoinhibition due to light saturation.

• Circadian Rhythm = does not seem to be a factor of midday depression

• Co2 Level = does not cause midday depression directly, but can be a cause of reduction in activated RuBP.

How to Prevent Midday Depression:

• Lowish [sic] VPD = 0.8-1.3 kPa

• Soil-Water Status = keep media moist, do not let it go lower than about 45% moisture content (by wet weight gravimetric basis; see link in my sig for more info on how to water)

• Light saturation = do not exceed 1,500-1,600 PPFD for cannabis.

• Active RuBP = keep temps at or below 30'C if using Co2 and keep Co2 at or below 1,000 ppm.

• Misting Plants = when leafs are misted it helps increase stomatal conductance and Pn. I wrote earlier that I use an hour of dark at midday in the thought it will reduce the midday depression; well I now know the hour of dark is not of much help at all to reduce midday depression. However, the hour of dark is a great time to spray plants to increase stomatal conductance (and help prevent midday depression of PS II QE). If we use an hour of dark per daylength, or maybe two half-hour instances of darkness at which time we would mist the plants it could be helpful.

This graph shows three different daily (diurnal) Pnnet (net rate of photosynthesis), the first curve is a one-peak diurnal Pnnet, the second curve is a two-peak diurnal Pnnet, and the third curve is a one-peak diurnal Pnnet with drastic midday depression. I attached the PDF to this post, I scanned it yesterday from a huge book entitled "Handbook of Photosynthesis; 2nd Edition". The paper is not the best scan job and the first two pages should be ignored, start reading on page three. The text can be a bit hard to read but I had no problems, my 'CliffNotes' are above.

HTH

 

[VerdantGreen]

Now how about we talk about LED vs. HID

What if we were to think of a scale from 1-3 for the characteristics of a light source (Sun, LED, HID):

Ease of concealment (eyes and ears and power company and law enforcement)
Cost to operate (environmental)
Cost to operate (monetary and effort)
Initial cost
Effect on growth and quality
Yield possible per square foot


what else?

well done - apart from myself you are the first ive seen to cite environment as a factor to consider.

one major one that you missed is also heat, LED's generate tiny amounts of heat compared to HID and this means that grows are possible or more ideal in places where it would otherwise be too hot or need A/C

also HID lights are not as efficient at lower wattages. im pretty sure my 63 watt unit would give out more light and yield more than a 70watt HPS lamp.

V.

 

[secondtry]

Hey Mad.L,

Aw, come on 2ndtry, can we just get a bit empirical and do a grow? It can be stealth with an LED, no?

I will do that if the PPFD is reaches at least 1,300 PPFD from the LED panel at a distance of at least 8-10". I don't think the LED panels will reach that irradiance, I think it will probably take a 1,000 watt to reach 1,300-1,500 PPFD at a reasonable distance from canopy (and without greatly increasing leafs temperature).

Mad.L, wrote:

Tell me, is there anything to the idea of light penetration? I think that's what he's getting at with the proposed test.

Sure, that is what PPFDi is for, to understand incident PPFD within the whole canopy. However, younger leafs and leafs on top of the canopy generally photosynthesize at higher rates than lower leafs and older leafs. To measure light penetration we can use PPFDi, it accounts for leaf angle (horizontal to lamp) because the greater the leaf angle the less PPFD strikes each leaf, thus those photons continue to lower leafs (this has to due with diffusion, incident, etc); PPFDi also takes into account leaf density as the amount and/or placement of leafs. I have played with PPFDi trying to use leaf angle and leaf density represented on a 0-10 scale.

Generally the goal is to increase PPFDi (as long as PPFD is =< 1,500) . Thus if we increase PPFDi we can increase the effective light usage by the plant by using plant placement, LST, topping, leaf pruning, etc.

That said, a test of light penetration is very possible, however it seems a problem is the size/shape of leafs and whole canopy which has a very large effect upon PPFDi, thus PPFDi does not seem like a good method of comparison when buying a new lighting system. AFAIK PPFD is the best comparison method for laypeople like us when comparing LED vs HID. Using a grow test to compare LED vs HID adds way too many variables and results effected by said variables other than the light irradiance or spectral quality (SPD).

Does that make sense?

 

[secondtry]

Hey VG,

Mad,L wrote:

Now how about we talk about LED vs. HID

What if we were to think of a scale from 1-3 for the characteristics of a light source (Sun, LED, HID):

Ease of concealment (eyes and ears and power company and law enforcement)
Cost to operate (environmental)
Cost to operate (monetary and effort)
Initial cost
Effect on growth and quality
Yield possible per square foot


what else?

well done - apart from myself you are the first ive seen to cite environment as a factor to consider.

Huh? What about me? I always have stated LEDs are good in power/height limited environs


I am worried that you guys/gals are underestimating the loss in rate of photosynthesis (Pn)/yield/quality for an increase in other areas like stealth, heat issues, etc. I would not want to sacrifice Pn/yield/quality for ease of setup, or so I could use very low wattage lamps.

I think a comparison of LED vs HID needs to be conducted with very limited criteria, and those criteria need to be non-subjective (e.g., PPFD and SPD vs. PAS). Most of the items in Mad's list are subjective and some impossible to correctly quantify; thus they are not very useful for a comparison of LED vs HID in terms of their ability to grow cannabis. The items Mad,L listed are good to take into consideration but I don't think they should be a determining factor more than PPFD, unless the grower doesn't care about reaching max rates of photosynthesis, growth, yield, quality, etc., more so than the ability to grow with low wattage or to grow in a cabnet, etc.

All the best

 

[secondtry]

@ Mods:

What does a bothra have to do to get a sticky around here?

 

[secondtry]

LED vs HID using PPFD:


I was thinking about my recent post about LED and PPFD, and I realized I made it sound like a 400w HID can/will emit 1,300-1,500 PPFD as most 400w HIDs are commonly used (i.e. hung 8-12" from canopy). Ideally we would all use 1,300-1,500 PPFD but I know that isn't possible for lots of people. So it seems in order to test the PPFD (for example) of a 400watt lamp (either HPS or MH) and also the PPFD of (for example) one of LEDGirls big, new panels. If the PPFD of the LED panel when hung at a commonly used distance (a realistically usable distance like > 8") is the same or close to the same as the PPFD from commonly used 400w HID lamp and ballast (e.x. Hotirlux Super HPS hung at 8-12") then the LED panel should definitely be considered for use. However, both the 400w and LED panel are a worse choice than a lamp that emits 1,500 PPFD (e.g. a 1,000w HID), that is if power and space are not limiting factors. A 1,000w HID growing a single plant should be better than a 400w HID growing a single plant (in terms of PPFD).

HTH

 

[mad librettist]

2ndtry,

Using 1-10 on a subjective scale is how doctors assess pain.

That's pretty powerful analytical gear.

 

[renz]

I need a day or two to read up on the thread, but yeah I think there needs to be a bit more clarity as far as what a watt is in an led system, because no one seems to be bringing up their drive method, so efficiency could be low or regulation could be crappy.

Also, where are these LEDs coming from? And are power output ratings just based on multiplying a 5W LED times the number of LEDs? Because a 5W red LED at sane current for reliability usually doesn't make 5W.

Also,

http://www.darkertechnologies.com/image/20100222_growleds_proto2_40w.png

http://www.darkertechnologies.com/image/20100303_growleds_proto2_40w_built1.jpg

through

http://www.darkertechnologies.com/image/20100303_growleds_proto2_40w_built7.jpg

That's my second prototype design for a star LED chassis, 12 emitters, those are 5W cool white (blue w/ phosphor) and 660nm red. Needs the endplate hardware but they're functional. I'm building another bar just for 12 * 660nm red. 1.2A, power through the LEDs is 43W measured per bar. That's not an incredibly efficient heatsink but its enough for the job, and rugged.

Right now I'm running resistors on a 24V offline PSU, so the led strings and the current regulation is 75%, not great but I don't care at this point, its easy and its cheap, eventually I want to do integrated current regulating switchers.

If anyone wants me to fabricate them a similar setup to hold high efficiency star mounted LEDs (3 to 10W emitters), I wouldn't mind the work (I have a little CNC, those were pretty sloppy setups on non-mating parts, so if you get one it will be neater). You can get a 1A buck regulator module for $15 good for about 6 to 8 LEDs depending on type and power supply, and get 90%+ efficiency instead of the resistors like I'm using for 75%.

AND, if you guys organize a group buy on high output high efficiency LEDs, you can easily try this tech out for around half the cost of retail offerings. That's the expensive part, the hardware and passive cooling chassis (think heavy analog HID ballast heatsink chassis) doesn't cost much at all compared to the high output LEDs. That's about how much it cost me and I just built a few.

Back to catching up...

 

[renz]

Also yeah, if you are not in this for the long term efficiency payback, willing to waste some money figuring out something that works, don't waste your money on LEDs unless you can't use an HID setup, because the thermal benefits of distributed LED sources are real.

I wont be convinced until I see real side by side controlled experiments w/ lab grade LED equipment that can be monitored for power THROUGH THE LEDS, not pulled from the wall, for comparison against standard output HID systems. Pictures of plants budding is neat an everything but does anyone have any grams per watt numbers? Standard HID is like 3-4x more efficient at raw light output (UFO website just lies), so this is maybe more of an uphill battle than people want to think. But I think even 20% savings in power would be worth it in the long run. Something like 66% savings and low voltage input capabilities is an industry breaker, indisputably, *even* at these costs, yet everyone says they suck at budding, and no one is in a huge rush to convert. So I really have my doubts.

 

[secondtry]

Hello renz and welcome,

I wont be convinced until I see real side by side controlled experiments w/ lab grade LED equipment that can be monitored for power THROUGH THE LEDS, not pulled from the wall, for comparison against standard output HID systems. Pictures of plants budding is neat an everything but does anyone have any grams per watt numbers?

I agree comparing LED vs HID by watt is not valid, what I suggest (using PPFD) seems to be what you suggest too as "monitored for power THROUGH THE LEDS". I for one do not think a side-by-side is the way to go, far too many variables to account for, that is why PPFD is the best choice for us (well, weighted PPFD would be better but I need a spectroradiometer for that, not a quantum sensor).

If someone did do a side-by-side grow and wanted to compare by weight of dried raw cannabis (ex. at 30-35% moisture content) then using "grams per PPFD DLI per days growing" seems reasonable method to me, or for a more fine grained comparison this could work: "grams per PPFD DLI per cubic foot of whole canopy per days growing", an example could be: 1 gram per 200 mol/day per 3 ft^3 whole canopy per 90 days (the day is veg and flower)

If LEDs of any technology can emit 1,300-1,500 PPFD at a reasonable distance from canopy I would be very, very, very surprised. That said, AFAIK a 400w or 600w HID doesn't emit 1,500 PPFD at reasonable distances either, but the HIDs should be emitting much greater PPFD than LED panel so it becomes a 'best of the worst' sitution in terms of choosing between (for example) a 400w HID and a 300w LED panel.

 

[mad librettist]

2ndtry,

grams per kilowatt hour is indeed relevant! How efficiently a grower turns electricity into weed is the whole idea.

I'm not sure I understand it fully, but it seems ppfd means "how good is the light". So having both of those figures is more helpful than just one alone, because now you are thinking in two dimensions, not just one.

I say get a third criterion. then a fourth. more data is better than less data.

 

[VerdantGreen]

Huh? What about me? I always have stated LEDs are good in power/height limited environs

what i dont understand is, what environs AREN"T power limited?
even if you can afford the electricity, you should be limiting your power consumption for environmental reasons anyway.

like i said before, for me, if i replace my 250 hps in my cab with a 205 watt LED unit and get better results over a few runs, that will prove it to me way more than any calculations or light meters could - because i have run the cab for a year or so with hps and cmh and basically pretty much maximised the yield i can get. if i run the same strains with the same soil in the same environment and get better results with LED then i dont see how anyone can argue with that (although im sure they will )

no-one knows 100% how plants use light and what wavelengths they utilise better than other afaik - so any light meter testing will not tell the full story imo. useful info for sure but not the answer.

V.

P.S. i will be starting the 205 watt LED in my 'quarters' cab in 2-3 weeks cant wait!

 

[secondtry]

2ndtry,

grams per kilowatt hour is indeed relevant! How efficiently a grower turns electricity into weed is the whole idea.

I don't want to turn this thread into this debate. There is a good thread in the indoor sub-forum on this topic. But for an accurate comparison we need the time of growing (days) and we don't measure kW, we would measure PPFD over a whole day (mol/day) because plants don't use kW, they use PPFD. Thus for an accurate comparison we should use PPFD. But still, comparing by yeild is really only valid for one grower, not between growers; there are too many variables which effect yield to use it as an accurate comparison between LED and HID. We know what PPFD cannabis wants, so that is how we should compare lamps.

MadL wrote:

I'm not sure I understand it fully, but it seems ppfd means "how good is the light". So having both of those figures is more helpful than just one alone, because now you are thinking in two dimensions, not just one.

PPFD is a counting of the photons within PAR range (400-700nm) landing in a square meter per second. Thus it's an accurate way to compare LED vs HID. PPFD could be considered to mean "how good is the light for growing cannabis". While gram per kW or gram per PPFD shows the skill of the grower more so than the quality of the lamp; that is why I don't like using gram/per energy as a method to compare lamps.

If PPFD is below 1,500 than cannabis should not be at it's peak rate of photosynthesis. From 1,300-1,500 PPFD is good, ideal PPFD of around 1,500 increases growth and yield over lower irradiances.

Using gram per energy (ideally PPFD) per grow time (days) is a good way to do a side-by-side, and I agree more data is better. But if someone is comparing two lamps so she/he can buy one of them using PPFD to compare LED vs. HID is the best method short of weighting PPFD.

I say get a third criterion. then a fourth. more data is better than less data.

I agree, but we need to make sure the data is valid, and using energy as watts or Kw is not as accurate as PPFD, not even close. To compare lamps using PPFD is all we need, we don't need side-by-side grows because they come down to grower skill, etc, in terms of growing more so than the quality of the lamp.

 

[mad librettist]

But for an accurate comparison we need the time of growing (days) and we don't measure kW, we would measure PPFD over a whole day (mol/day) because plants don't use kW, they use PPFD

are you going to call my power company and tell them to start charging me in PPFD?

kilowatt hours is the input cost we are trying to keep down! Otherwise why bother looking at LED?

I'm with you often 2ndtry, but you got me real confused here. What do i care about PPFD if in the end I will be financially and environmentally screwed by implementing a technology?

I like the PPFD thing, really. But in the end, the calculus is "what's it going to cost me to make a gram of weed". Maybe look at potency on the side and other qualities as well. But don't leave out an estimation of cost/benefit. That's the whole point bro!

at least, in situ it is.


So let's get you a hypothesis, and let's test it. In vivo. And i say measure at the outlet, because the driver technology can't be separated any more than you can discount the digital ballast.

I say do a comparison with clones of the best LED array and a 250w hps. And a 500 for good measure, or a 1k. If there is a discrepancy between your predictions based on PPFD and the real world result, that would be a breakthrough in itself.