MMJ Dreaming 99
Well-Known Member
I thought I read in a thread that CMH was killing it in verg versus HPS or COB or QB.
My impression is QB boards may be the fastest in veg.
My impression is QB boards may be the fastest in veg.
Did someone post on a thread that 315 Watt CMH cut a week out of veg?
- Thread starter MMJ Dreaming 99
- Start date
frankEinstein
Member
frankEinstein
Member
It does
wietefras
Well-Known Member
Why would QB be faster than COBs? It's exactly the same light.
What really matters for speed is the intensity, not the spectrum. Although there is more than speed to consider. The bigger amount of red in HPS gives you some more stretch. Which I never liked, but people use 90 CRI COBs with the same extra stretching effect and they seem to love it.
churchhaze
Well-Known Member
Exactly.. Those are the wavelengths that I think make HPS really shine! (pun intended)
Clearly there are many that disagree. I do agree that everything over 750nm is basically useless... The reason I like 3000k 80cri is all the "useless" yellow. That being said, I've never tried 90cri chips.
Whenever I see R+B side by side with HPS, the HPS plants are always taller and better looking, regardless of the intensity of the R+B. Imo, people should be trying to figure out what's right about HPS rather assuming everything is wrong with it.
MichiganMedGrower
Well-Known Member
lol I have already figured out what is right about HPS.
A big fat band of penetrating yellow light along with a bit of deep red which flowering plants love. Again proof that Quantity of photons trumps quality of spectrum.
The infra red heat waves drives transpiration hard which is beneficial, but unfortunately the direct heat is hard to manage indoors.
Last edited:
DemonTrich
Well-Known Member
Nah, cmh are crap. Stick with your 1k bulbs and spend hundreds more to get the same yield with cmh.
Lol
Lol
churchhaze
Well-Known Member
True until someone puts out an efficient light that produces only a narrow band at 699nm (all quantity, all PAR photons), than power (and thus spectrum) becomes more important than quantity.
To fix that spectrum, each photon would need to have more energy. Power is a function of quantity and spectrum and the spectrum can't be whatever you want it to be.
There's really no reason to favor PPF over power. I still think calculating PPF is an unnecessary step for weed growers. W of PAR tells you the exact same thing and only requires the grower to roughly know their efficiency..
Last edited:
wietefras
Well-Known Member
No, it doesn't. You can have the same PAR watts and still have a very different PPF. Up to 40% different even.
If anything, it's useless to look at PAR W or radiometric efficiency. Just divide the lumen/lux by the lumen to PPF conversion factor.
churchhaze
Well-Known Member
That doesn't mean that ppf is more useful than power, it just means that neither of them tell you the whole story without SPD. That's why I gave the hypothetical example of 699nm photons. In that case PPF is a useless measurement on its own as making some of those photons blue (and other colors under 699nm) while keeping PPF constant would mean more power. .
Considering neither power nor PPF tells you the whole story, why not just use power. Lumen to PPF conversion factor tells me nothing intuitively about how well the lamp is performing compared to the theoretical max, but efficiency does.
Last edited:
Yes there are obvious extreme spectrum scenarios that just plain fail. Try growing a plant under blue cobs (without phosphor coating), high electrical efficiency but I'd bet the plant would not be happy.
I can easily ballpark how many watts of lighting I need for a grow space based on the type of light source without calculating PPF. I do however need an understanding of the efficiency and spectrum of a given light source.
churchhaze
Well-Known Member
That's exactly what I'm talking about though. Because only 15-20% blue is ever needed, it makes it seem like PPF is more important than power but without knowing SPD, neither power nor PPF tell you what you need to know. If you have 0% blue, then it's PPF that becomes the more misleading value. If you have 100% blue, then power becomes the misleading value.
However, power OR PPF combined with SPD will both tell you what you need to know and thus you could in practice use either and there's no hard reason to use one over the other.
I was using those extremes for the sake of example. Higher ppf (while keeping power constant) will only help if you have too much blue or not enough red while higher power (while keeping ppf constant) will only help if you lack blue (or higher energy photons in general). ( oversimplified i know, but true for the most part)
Last edited:
wietefras
Well-Known Member
Because, PPF is a lot more accurate than efficiency. PPF/W is a much better metric than efficiency for measuring how the plants use the light. There really is zero room for discussion there.
If you want to improve on PPF and incorporate how the plant deals with the SPD then you could go for YPF.
Efficiency is by far the least useful (possibly 40% off), PPF is much more useful and YPF is potentially more useful still.
Don't just consider COBs, but also look at mono's. Efficiency is especially useless with those.
Why even bother about efficiency? What's the benefit of using efficiency instead of PPF? Just multiply watts by umol/J and you have the PPF. Is that so much more work than dividing lumen/LER? And in the latter case you still know nothing really. You might be 40% off.
churchhaze
Well-Known Member
I already answered this. You might also be 40% off. Quantity within PAR range is clearly not all that matters or it would imply a pure 699nm SPD is ideal. There's nothing inherently more useful about using PPF over power other than the fact that plants don't want more than 20% blue.
Last edited:
churchhaze
Well-Known Member
The benefit of using efficiency over umol/J is one intuitively gives you an idea of how well it's working compared to the theoretic maximum. umol/J does not.
Olive Drab Green
Well-Known Member
I use full spectrum 3500k daylight (80 and 90 CRI) and get about 1013 PPFD at 18”. I mean, I would roll with full-spectrum, but what else could possibly matter except for useable photons for a plant? Maybe the outer spectra more properly amplify the PAR range? Either way, if a plant can’t use a photon, I imagine that photon is worthless aside from how it impacts the usable spectrum.
Edit: Plus IR and UV, of course.