Gavita DE vs. CMH 630w systems: pros and cons of both?

[luxcultivars]

I just spent the weekend reading the CMH threads and really love what I'm reading about them. I'm curious why a person might lean towards one or the other type? Why is Gavita so popular these days?

Is CMH just too new to compete right now? The lack of basic options like air-cooled hoods and 120v functionality are glaring. Also clear is that anyone who lights a fire under their ass and designs good CMH systems for a vaguely fair price is going to get rich.

I love the 315w CMH but it is considerably more expensive to outfit 2 - 8'x11' rooms with those, so the 630w double-bulb versions of CMH seem best for me. I love the DimLux in particular due to the dimming and controller options. Why Sun Systems can't include a basic 50% dim function baffles me. In general I'm only interested in plug and play; I am not building/wiring 10+ CMH lights. I have enough other projects going on.

Anyway. Am I missing something about those Gavitas? I have seen the graphs with that hot spot and that doesn't appeal much to me. But maybe I'm missing something?

 

[Scrappy-doo]

Heat is not much of an issue with the 315 cdm's even without a vented hood. I have 3 cycloptics I'm running and they're fairly easy to cool.

 

[HenDokuYaku]

I'm using both the 1k DE Dimlux and the 630w double bulb. I am really impressed with the 630w. It looks as bright as the 1ks, except I haven't done an individual ppfd measurements on the lights individually, but I didn't have too much trouble evening the light intensity. I have about a 3-1 ratio. 1ks to 630w. Let me know if you have any questions.

I just spent the weekend reading the CMH threads and really love what I'm reading about them. I'm curious why a person might lean towards one or the other type? Why is Gavita so popular these days?

Is CMH just too new to compete right now? The lack of basic options like air-cooled hoods and 120v functionality are glaring. Also clear is that anyone who lights a fire under their ass and designs good CMH systems for a vaguely fair price is going to get rich.

I love the 315w CMH but it is considerably more expensive to outfit 2 - 8'x11' rooms with those, so the 630w double-bulb versions of CMH seem best for me. I love the DimLux in particular due to the dimming and controller options. Why Sun Systems can't include a basic 50% dim function baffles me. In general I'm only interested in plug and play; I am not building/wiring 10+ CMH lights. I have enough other projects going on.

Anyway. Am I missing something about those Gavitas? I have seen the graphs with that hot spot and that doesn't appeal much to me. But maybe I'm missing something?

 

[luxcultivars]

Thanks for responding, guys. I'm pretty much just asking what the major difference is between the two types; why would a person gravitate towards either Gavitas or 630w CMHs in a 4 or 5 fixture-per-room situation?

Scrappy, I wish I could afford 16 cycloptics! Those are so sweet. Just too expensive at this scale for me.

 

[HenDokuYaku]

Thanks for responding, guys. I'm pretty much just asking what the major difference is between the two types; why would a person gravitate towards either Gavitas or 630w CMHs in a 4 or 5 fixture-per-room situation?

Scrappy, I wish I could afford 16 cycloptics! Those are so sweet. Just too expensive at this scale for me.

The difference is the spectrum. There is more red in the HPS DE
and CRI (color rendering index). That may or may not matter to plants at all, but CRI is much higher on the CMH. The big difference is the spectrum is much more complete like the sun with the CMH.

 

[Beta Test Team]

Thanks for responding, guys. I'm pretty much just asking what the major difference is between the two types; why would a person gravitate towards either Gavitas or 630w CMHs in a 4 or 5 fixture-per-room situation?

Scrappy, I wish I could afford 16 cycloptics! Those are so sweet. Just too expensive at this scale for me.

In terms of the lamps, like the person above wrote, the major difference is spectra, with the Philips GreenPower 315w and Mastercolor Elite 942 315W having much better spectra for all stages of plant growth than the Philips DE HPS.

In terms of luminaires, the major difference is efficiency in turning watts (power) into PAR range photons (energy), with the Philips DE HPS luminaire being the most efficient (be it luminaires by Gavita or ePapillion).

In terms of irradiance uniformity, the 630W CMH luminaire (e.g. Double dPapillion) is better for two reasons: (1) the Gavita reflector has a pretty extreme hot spot, that is, it doesn't provide very uniform irradiance at canopy; and (2) because you'd use more 630W luminaires you'll have more points of radiation, which in turn means better uniformity over the canopy.

In terms of why people like Gavita DE HPS so much these days, I think it's mostly about confirmation bias and marketing by Gavita, as well as 'monkey see monkey do' (not trying to be rude here), vs. using ePapillion DE HPS. Because the ePapillion has considerably better uniformity for reduced hot spot vs. Gavita, and emits about 1% more PAR range energy (umol/s) than Gavita.

So long story short, in my opinion: if money isn't a factor, use only Double dPapillion (with a 1:1 mix of Greenpower and 942, or only 942). But if money is a factor, use a mix of ePapillion and Double dPapillion, ideally with around 1:1 ratio by wattage.

If the PPF (which is the same thing as PPFD) is the same from the Philips 315W CMH luminaires and Philips DE HPS luminaires, the former would give better plant growth and quality, and very likely better yield, simply due to spectra differences.

For what it's worth, Greenbeams is now selling the fixture for $275, so if you can source lower cost ballast and lamp (such as from Advanced Technology Solutions), you can use Greenbeams plug-and-play style. For example, Greenbeams fixture + Wellthink ballast (runs on 120V or 240v) + lamp.

 

[Beta Test Team]

Oh yea, about PPF (the same thing as PPFD), both Gavita and ePapillion are way off the mark when they suggest 1,000 as the goal. You want between 700-800 at all times, with around 700 for veg and 800 for flowering (to account for daylength in terms of DLI), with the outside range of 600-900.

Not only is 1,000 PPF too much when its provided all day long, with the way Gavita and ePapillion calculate number of fixtures they overshoot 1,000 by normally at least 100, so in reality, some areas of the canopy get >1,100 PPF, which is way too much radiation all day long.

The claim of 1,000 PPF as ideal is flawed, based upon a flawed study on Cannabis. Who's authors now use 700 PPF to grow Cannabis, not the 1,500 PPF they suggested(!) as ideal from their flawed study.

 

[luxcultivars]

Thank you! Great information, and your contributions to all of these lighting threads is much appreciated, BTT.

 

[bluerock]

I just spent the weekend reading the CMH threads and really love what I'm reading about them. I'm curious why a person might lean towards one or the other type? Why is Gavita so popular these days?

Is CMH just too new to compete right now? The lack of basic options like air-cooled hoods and 120v functionality are glaring. Also clear is that anyone who lights a fire under their ass and designs good CMH systems for a vaguely fair price is going to get rich.

I love the 315w CMH but it is considerably more expensive to outfit 2 - 8'x11' rooms with those, so the 630w double-bulb versions of CMH seem best for me. I love the DimLux in particular due to the dimming and controller options. Why Sun Systems can't include a basic 50% dim function baffles me. In general I'm only interested in plug and play; I am not building/wiring 10+ CMH lights. I have enough other projects going on.

Anyway. Am I missing something about those Gavitas? I have seen the graphs with that hot spot and that doesn't appeal much to me. But maybe I'm missing something?

The heart of the matter is simple: a 1000w DE is going to blow away a 315w bulb in all contest. Even if you double up the 315w bulbs, you are still not getting the intensity produced by a 1000w, be it DE or SE.

Gavita is popular because they make excellent products and they get them on the store shelves so that people can buy them. A Gavita DE will produce greater yield than any identical wattage SE simply because they produce more light. It's not even arguable; see what commercial growers are doing, they don't waste time or money on things that won't increase production.

 

[billyboat]

In terms of why people like Gavita DE HPS so much these days, I think it's mostly about confirmation bias and marketing by Gavita, as well as 'monkey see monkey do' (not trying to be rude here), vs. using ePapillion DE HPS. Because the ePapillion has considerably better uniformity for reduced hot spot vs. Gavita, and emits about 1% more PAR range energy (umol/s) than Gavita.

I have rooms with Epap's, Nano's, and my buddy switched from epaps to gavitas, and my Epaps are the lower yielding fixtures in all of my rooms. They just don't penetrate as much as my other fixtures.

 

[Beta Test Team]

In terms of why people like Gavita DE HPS so much these days, I think it's mostly about confirmation bias and marketing by Gavita, as well as 'monkey see monkey do' (not trying to be rude here), vs. using ePapillion DE HPS. Because the ePapillion has considerably better uniformity for reduced hot spot vs. Gavita, and emits about 1% more PAR range energy (umol/s) than Gavita.

I have rooms with Epap's, Nano's, and my buddy switched from epaps to gavitas, and my Epaps are the lower yielding fixtures in all of my rooms. They just don't penetrate as much as my other fixtures.

Just in terms of physics, the concept and use of the term "penetration" is often incorrect in the Cannabis world, I think. What I mean is if the umol/s/inch^2 in PAR range for Gavita and ePapillion is the same, so will be the 'penetration' (because both use the same Philips lamp). A proper comparison between the two fixtures (and Nanolux, if using the same Philips lamp) would be to ensure the irradiance is the same, with a quantum sensor.

The thing about Gavita is the reflectors have considerably greater hot spot (i.e. spike in irradiance relative to the rest of the 'foot pint'). below the lamp vs. ePapillion. As shown in this figure:

So depending upon how the fixtures are positioned, the room dimensions, and distance to canopy, Gavita is likely to have greater irradiance directly below the lamp vs. ePapillion. This is likely why you're seeing greater yield from Gavita. That is, not because they're inherently better than ePapillion, just that without optimal placement and use (via. quantum sensor), plants directly below Gavita get greater irraidiance than plants directly below ePapillion.

And for a dense canopy, the vast majority of spectra wavebands penetrating (i.e. transmittance) through leaves are NIR (far red radiation) and IR, with relatively little green range radiation transmitting through leaves, and nearly all blue and red range radiation is absorbed by the leaves. Along with green range radiation having greatest reflection within PAR range (because Cannabis leaves reflect around 15%-30% of the green radiation), so some of those 'green' photons will reflect downward into the canopy, to join transmitted photons from the green, NIR and IR ranges. See these example graphs of narrow leaflet Cannabis genotype (adaxial = top of leaf):

 

[Beta Test Team]

The heart of the matter is simple: a 1000w DE is going to blow away a 315w bulb in all contest. Even if you double up the 315w bulbs, you are still not getting the intensity produced by a 1000w, be it DE or SE.

Gavita is popular because they make excellent products and they get them on the store shelves so that people can buy them. A Gavita DE will produce greater yield than any identical wattage SE simply because they produce more light. It's not even arguable; see what commercial growers are doing, they don't waste time or money on things that won't increase production.

You're looking at the wrong issue, I think. The only thing that matters is PPF (i.e. intensity) at canopy (not fixture radiance), in terms of plant growth (spectrum notwithstanding, where CMH is far better than HPS in most cases).

So a Gavita is not better than 315W CMH if the PPF at canopy is the same for both. And it's very possible to provide the same PPF with e.g. Double dPapillion, Gavita DE HPS, ePapillion, and various SE HPS fixtures; the only issue is proper number and placement of fixtures, where one would need more CMH wattage (and so fixtures), likely 0.5x to 1.5x as much, to provide the same PPF as DE HPS, due to total energy output (umol/s in PAR range) of each fixture and photosynthetic efficiency of the lamps (with DE HPS being greater than CMH, due to the greater relative red range % output from DE HPS than CMH).

The reason commercial growers often choose DE HPS is due to start up costs (fewer DE HPS fixtures are required, if one doesn't care about getting optimal uniformity), relamping costs (see useful life span and number of lamps), and electrical usage (see photosynthetic efficiency of lamps, as umol/s in PAR range per input watt).

All of the above however doesn't consider spectra. And if spectra is considered, CMH is better for plant growth and quality, assuming PPF is the same for all fixtures under consideration.

 

[bluerock]

You're looking at the wrong issue, I think. The only thing that matters is PPF (i.e. intensity) at canopy (not fixture radiance), in terms of plant growth (spectrum notwithstanding, where CMH is far better than HPS in most cases).

So a Gavita is not better than 315W CMH if the PPF at canopy is the same for both. And it's very possible to provide the same PPF with e.g. Double dPapillion, Gavita DE HPS, ePapillion, and various SE HPS fixtures; the only issue is proper number and placement of fixtures, where one would need more CMH wattage (and so fixtures), likely 0.5x to 1.5x as much, to provide the same PPF as DE HPS, due to total energy output (umol/s in PAR range) of each fixture and photosynthetic efficiency of the lamps (with DE HPS being greater than CMH, due to the greater relative red range % output from DE HPS than CMH).

The reason commercial growers often choose DE HPS is due to start up costs (fewer DE HPS fixtures are required, if one doesn't care about getting optimal uniformity), relamping costs (see useful life span and number of lamps), and electrical usage (see photosynthetic efficiency of lamps, as umol/s in PAR range per input watt).

All of the above however doesn't consider spectra. And if spectra is considered, CMH is better for plant growth and quality, assuming PPF is the same for all fixtures under consideration.

If you are growing lettuce, then canopy penetration is not an issue. In the case of multiple 24"-30" cannabis plants, it very much matters to facilitate better development of the lower flower sites. With the higher wattage bulb, the intensity at depth is going to be greater than the lower wattage bulb and it will provide said intensity over a larger area.

I believe spectrum to be overrated and largely subjective. If the genetics are there, the difference is marginal. Back in the bad old days, growers were known to use low pressure sodium as it has the highest intensity per watt of all lighting. Reportedly, if it was used alone, the plants had a deformed look but the quality was there.

If you can cite any scientific studies showing that spectrum produces anything other than marginal differences in cannabis quality, I would be glad to read them. Also, I have not personally observed any increase in quantity by using "better spectrum" lighting even given canopy PPF uniformity from whatever bulb that was tested. (Disclaimer: I have not tested CMH. It is not available locally nor am I aware that it is used commercially on anything other than a limited basis, if that. The use of HPS DE is not about Gavita marketing: it is about achieving the best overall results for the least expense. If CMH was commercially practical and superior, it's use would be widespread. It isn't.)

 

[luxcultivars]

If you are growing lettuce, then canopy penetration is not an issue. In the case of multiple 24"-30" cannabis plants, it very much matters to facilitate better development of the lower flower sites. With the higher wattage bulb, the intensity at depth is going to be greater than the lower wattage bulb and it will provide said intensity over a larger area.

I believe spectrum to be overrated and largely subjective. If the genetics are there, the difference is marginal. Back in the bad old days, growers were known to use low pressure sodium as it has the highest intensity per watt of all lighting. Reportedly, if it was used alone, the plants had a deformed look but the quality was there.

If you can cite any scientific studies showing that spectrum produces anything other than marginal differences in cannabis quality, I would be glad to read them. Also, I have not personally observed any increase in quantity by using "better spectrum" lighting even given canopy PPF uniformity from whatever bulb that was tested. (Disclaimer: I have not tested CMH. It is not available locally nor am I aware that it is used commercially on anything other than a limited basis, if that. The use of HPS DE is not about Gavita marketing: it is about achieving the best overall results for the least expense. If CMH was commercially practical and superior, it's use would be widespread. It isn't.)

I was under the impression that the real benefit of the 'better spectrum' with CMH is the electrical efficiency that comes along with it. Less total watts needed to provide adequate light for healthy growth, less heat...?

Seems to me that CMH isn't popular solely because of the high initial investment expense, not due to performance or light penetration issues. People using them aren't growing lettuce, but they are growing some damned fine cannabis, and the lower buds on 3 foot plants are developing just fine. Where did you get the impression that they weren't?

 

[Beta Test Team]

If you are growing lettuce, then canopy penetration is not an issue. In the case of multiple 24"-30" cannabis plants, it very much matters to facilitate better development of the lower flower sites. With the higher wattage bulb, the intensity at depth is going to be greater than the lower wattage bulb and it will provide said intensity over a larger area.

You're missing the point of my post to the other member, I think. That is, if PPF at the canopy is the same for two different fixtures, and all other factors are the same (e.g. wall reflectivity), the 'penetration' will be the same. This is about physics of radiation.

Area doesn't factor into 'penetration,' in the context of the posts you're referring to above.

I believe spectrum to be overrated and largely subjective.

Then I would suggest you read some of our threads in my signature, specifically see the ones about "absorptance spectra," "action spectra" and "RQE."

If you can cite any scientific studies showing that spectrum produces anything other than marginal differences in cannabis quality, I would be glad to read them.

I can and have already a few times here at this site, for example here are two:
https://www.icmag.com/ic/showthread.php?t=302671
https://www.icmag.com/ic/showpost.php?p=6575750&postcount=22

And Cannabis isn't unique in terms of higher plants, that is, you can look to other C3 plants similar to Cannabis to see how spectra affects various physiological responses to radiation. In most cases similar responses would be found in Cannabis, as well.

Also, I have not personally observed any increase in quantity by using "better spectrum" lighting even given canopy PPF uniformity from whatever bulb that was tested. (Disclaimer: I have not tested CMH. It is not available locally nor am I aware that it is used commercially on anything other than a limited basis, if that. The use of HPS DE is not about Gavita marketing: it is about achieving the best overall results for the least expense. If CMH was commercially practical and superior, it's use would be widespread. It isn't.)

If you're not measuring PPF at canopy then comparing different spectra affects on yield is not really possible, because radiation intensity is one of the (if not the) most important factor (e.g. even with an optimized spectrum if PPF is too low results will be poor).

The only reasons CMH use isn't widespread commercially are what I listed above, which as you also pointed out, such as about start-up costs and short term ROI, not about what is the best for plant growth. If you look at plant science research labs (at colleges and universities), it's CMH or a mix of MH and HPS that's used as HID in plant growth chambers, not solely HPS (SE or DE), because the effect of spectrum is an important consideration, and said institutions don't care nearly as much about issues such as ROI and start-up costs.

 

[bluerock]

I was under the impression that the real benefit of the 'better spectrum' with CMH is the electrical efficiency that comes along with it. Less total watts needed to provide adequate light for healthy growth, less heat...?

Seems to me that CMH isn't popular solely because of the high initial investment expense, not due to performance or light penetration issues. People using them aren't growing lettuce, but they are growing some damned fine cannabis, and the lower buds on 3 foot plants are developing just fine. Where did you get the impression that they weren't?

Electrical efficiency? Adequate? HPS DE is superior precisely because it is more electrically efficient than CMH. And "damned fine cannabis"? You can grow the same with T5s....but you won't touch the yield obtained by higher intensity lighting.

You're missing the point of my post to the other member, I think. That is, if PPF at the canopy is the same for two different fixtures, and all other factors are the same (e.g. wall reflectivity), the 'penetration' will be the same. This is about physics of radiation.

Area doesn't factor into 'penetration,' in the context of the posts you're referring to above.


Then I would suggest you read some of our threads in my signature, specifically see the ones about "absorptance spectra," "action spectra" and "RQE."


I can and have already a few times here at this site, for example here are two:
https://www.icmag.com/ic/showthread.php?t=302671
https://www.icmag.com/ic/showpost.php?p=6575750&postcount=22

And Cannabis isn't unique in terms of higher plants, that is, you can look to other C3 plants similar to Cannabis to see how spectra affects various physiological responses to radiation. In most cases similar responses would be found in Cannabis, as well.


If you're not measuring PPF at canopy then comparing different spectra affects on yield is not really possible, because radiation intensity is one of the (if not the) most important factor (e.g. even with an optimized spectrum if PPF is too low results will be poor).

The only reasons CMH use isn't widespread commercially are what I listed above, which as you also pointed out, such as about start-up costs and short term ROI, not about what is the best for plant growth. If you look at plant science research labs (at colleges and universities), it's CMH or a mix of MH and HPS that's used as HID in plant growth chambers, not solely HPS (SE or DE), because the effect of spectrum is an important consideration, and said institutions don't care nearly as much about issues such as ROI and start-up costs.

I'm sorry, but PPF at canopy for two different fixtures does not take into consideration what happens below canopy. That is dependent on both the wattage and intensity of (primarily) the bulbs in question. As I am sure you would agree.

As to your cited information, I totally agree that UV marginally improves quality. This is well documented by amateur and professional alike. The study examining cannabis leaves, well, we both agree that it is flawed.

"radiation intensity is one of the (if not the) most important factor (e.g. even with an optimized spectrum if PPF is too low results will be poor)." Could not agree more. Hence, the reason that HPS DE of higher wattage (and subsequent intensity) trumps CMH.

Short term ROI? No. If the improvement derived by the utilization of CMH were materially significant, they would be everywhere. While I haven't checked recently, I don't believe that there is even a digital ballast available for CMH. Why not? That's a rhetorical question.

Hortilux states that their "daylight blue" bulb is an ivory tower favorite. And yet, it is not used by commercial growers to any significant degree. That's great that researchers continue to research. Perhaps they will one day develop a commercially viable CMH. Until then, HPS DE will continue to be the primary choice of commercial usage for black market, gray market, and supplementary lighting in greenhouses.

Furthermore, since you called out whazzup on his "biased" affiliation with Gavita, I must question your own bias. Do you have a vested interest in the "success" of CMH lighting?

 

[Beta Test Team]

I was under the impression that the real benefit of the 'better spectrum' with CMH is the electrical efficiency that comes along with it. Less total watts needed to provide adequate light for healthy growth, less heat...?

Seems to me that CMH isn't popular solely because of the high initial investment expense, not due to performance or light penetration issues. People using them aren't growing lettuce, but they are growing some damned fine cannabis, and the lower buds on 3 foot plants are developing just fine. Where did you get the impression that they weren't?

Electrical efficiency? Adequate? HPS DE is superior precisely because it is more electrically efficient than CMH. And "damned fine cannabis"? You can grow the same with T5s....but you won't touch the yield obtained by higher intensity lighting.

Lux is correct, the Philips Greenpower 315W CMH lamp is very efficient in terms of converting watts to radiant PAR range photons (umol/s). That is, Philips Greenpower 315W CMH is 1.91 PAR range umol/s per watt, while the DE HPS used by Gavita and ePapillion (which I think is rebradned Philips, but could be wrong) is 2.1, so the DE HPS is about 9.05% more efficient. Lux didn't write the CMH is more efficient than the DE HPS, only that the CMH (from Philips) is very efficient, and that's true, it's more efficient than SE HPS, for example.

And this issue is only about cost of electricity, not better plant growth, because like I have written a few times, it's PPF at canopy that matters in terms of plant growth. So all it means when one lamp is more efficient than another is fewer fixtures would be needed to achieve the same PPF (in a simple example).

Also, Lux's point about heat is not to be dismissed, due to lower heat load in the grow room, so less cooling needs for CMH vs. DE HPS, when PPF is the same (due to less IR from CMH than DE HPS). The reduced cooling needs of the CMH helps offset the increased efficiency of the DE HPS, in terms of electricity usage.

If PPF is the same for CMH and DE HPS, so will the yield be very close. So it's not correct to state DE HPS out yields CMH, or other HID types, as long as PPF is the same. I think you're paying far too much attention to the source radiance, not canopy irradiance.

You're missing the point of my post to the other member, I think. That is, if PPF at the canopy is the same for two different fixtures, and all other factors are the same (e.g. wall reflectivity), the 'penetration' will be the same. This is about physics of radiation.

Area doesn't factor into 'penetration,' in the context of the posts you're referring to above.

Then I would suggest you read some of our threads in my signature, specifically see the ones about "absorptance spectra," "action spectra" and "RQE."

I can and have already a few times here at this site, for example here are two:
https://www.icmag.com/ic/showthread.php?t=302671
https://www.icmag.com/ic/showpost.ph...0&postcount=22

And Cannabis isn't unique in terms of higher plants, that is, you can look to other C3 plants similar to Cannabis to see how spectra affects various physiological responses to radiation. In most cases similar responses would be found in Cannabis, as well.

If you're not measuring PPF at canopy then comparing different spectra affects on yield is not really possible, because radiation intensity is one of the (if not the) most important factor (e.g. even with an optimized spectrum if PPF is too low results will be poor).

The only reasons CMH use isn't widespread commercially are what I listed above, which as you also pointed out, such as about start-up costs and short term ROI, not about what is the best for plant growth. If you look at plant science research labs (at colleges and universities), it's CMH or a mix of MH and HPS that's used as HID in plant growth chambers, not solely HPS (SE or DE), because the effect of spectrum is an important consideration, and said institutions don't care nearly as much about issues such as ROI and start-up costs.

I'm sorry, but PPF at canopy for two different fixtures does not take into consideration what happens below canopy. That is dependent on both the wattage and intensity of (primarily) the bulbs in question. As I am sure you would agree.

No, I would not agree, that's my whole point. If PPF is the same at canopy, so will PPF be below the canopy if the same spectrum is used for both luminaires (due to how leaves absorb, reflect, and transmit various wavebands).

And if the spectra are not the same for two different luminaires, but PPF is the same at canopy, then PPF below canopy will also be very similar.

You're paying too much attention to the lamp wattage, I think. What matters is PPF at canopy. So if you're using e.g. 600W and 1,000W, the latter would be farther from the canopy to provide the same PPF at canopy as the former, and both would provide the same 'penetration' into the canopy.

For closed canopies (like SCROG) there is very little penetration of wavebands other than NIR, IR, and green ranges.

As to your cited information, I totally agree that UV marginally improves quality. This is well documented by amateur and professional alike. The study examining cannabis leaves, well, we both agree that it is flawed.

The second study looked at effects of spectra on THC production, as well. And while it's flawed the findings are not without value. It goes to show the various wavebands affect plant quality.

radiation intensity is one of the (if not the) most important factor (e.g. even with an optimized spectrum if PPF is too low results will be poor).

Could not agree more. Hence, the reason that HPS DE of higher wattage (and subsequent intensity) trumps CMH.

Again, it's not about wattage, it's about PPF at canopy. So if the DE HPS and CMH are used at the same PPF at canopy DE HPS wouldn't trump CMH, the DE HPS would simply be farther away from the canopy.

Short term ROI? No. If the improvement derived by the utilization of CMH were materially significant, they would be everywhere. While I haven't checked recently, I don't believe that there is even a digital ballast available for CMH. Why not? That's a rhetorical question.

I suggest you read rive's thread on CMH, in terms of ballast technology.

About short term ROI, that is in fact a major reason CMH aren't used as commonly commercially, due to their start-up costs which are considerable, considering how many luminaires are needed to provide ideal PPF (e.g. for Cannabis, that's between 700-900, with min-max of 600-1,000, depending upon photoperiod hours).

Hortilux states that their "daylight blue" bulb is an ivory tower favorite. And yet, it is not used by commercial growers to any significant degree. That's great that researchers continue to research. Perhaps they will one day develop a commercially viable CMH. Until then, HPS DE will continue to be the primary choice of commercial usage for black market, gray market, and supplementary lighting in greenhouses.

Any business person worth their salt would never use that Hortlix Blue lamp, or any DE MH, simply due to relamping costs at useful lifespan of between 2,000-5,000 hours. This goes back to the ROI issue.

My point about research labs is they use the best spectrum for plant studies, that is, if DE HPS provided the best spectrum that's what they would use. And there is already a commercially viable CMH, it's the Philips Greenpower and MasterColor Elite 942. The main issue is manufacturers MSRP for their luminaires, not the technology.

Furthermore, since you called out whazzup on his "biased" affiliation with Gavita, I must question your own bias. Do you have a vested interest in the "success" of CMH lighting?

No, I do not. I simply prefer to rely on science, not marketing, to make choices and form opinions. And I for one think Gavita makes a great product, as does ePapillion, but I also know many claims made by them, and their devotees, are not factually correct.

 

[luxcultivars]

Hi, Bluerock. This is why I started this thread: to discuss the differences between these two types. You seem, err, close to veering into hostility, so... maybe lighten up a bit? Just a thought. I have a hard time learning from people who need to start insulting others to make their point. BTT has no vested interest in CMH. That's a serious stretch.

Electrical efficiency? Adequate? HPS DE is superior precisely because it is more electrically efficient than CMH. And "damned fine cannabis"? You can grow the same with T5s....but you won't touch the yield obtained by higher intensity lighting.

You seem to be missing my point. If a 630w double-bulb CMH achieves (weight and quality-wise) what a 1000w Gavita does (as claimed by some in the 315w CMH thread), the Gavita is not a 'better' or more efficient fixture. It consumes ~30% more electricity, generates ~1/3 more heat. To be correct with that assessment you'd need to be pulling in 1/3 more weight than a person with a 630w CMH, and... I seriously doubt that is happening. This is assuming quality is a given with a dialed-in feeding regimen.

Understand that I don't have any CHM fixtures. yet. I am re-designing my entire scene and the 630w CMH potentially looks like a great option (aside from the steep initial investment). I am open to other types like the Gavitas, but the feedback that I am getting from friends in the field is that they are overhyped and overrated. So here I am investigating it further.

As far as lower bud development goes, I think you are possibly a bit confused about how plants actually process energy via photosynthesis and distribute it to the entire plant rather than just the tops which are exposed to the most light. A few years ago on another forum this was discussed in detail and a side by side was done where the lower buds were actually screened from direct light on half of a plant... and they developed just as well as the buds that weren't screened. The only difference was that they were slightly lighter green. Density was the same.

I realize that this is anecdotal, but that result matches what I have seen over 20 years of growing. Some strains are definitely prone to looser lower buds, but it has little to do with the actual light intensity down there provided the plant itself is being hit with full intensity at the canopy top.

I find it highly unlikely that a CMH would have such an insufficient penetration that it would measurably negatively affect lower flower development.

 

[bluerock]

A genuine scientific effort would by definition include all commonly utilized lighting to determine not only the best available device, but also as a control.

So you are stating that as long as the PPF at canopy is equal, the light output beyond that range is, in fact, linear regardless of wattage or varying lumen output of different bulb types?

 

[bluerock]

That last is for Beta. And Lux, I am not veering into hostility, merely questioning your assertions. The very essence of debate. No offense intended.