3000k vs 4000k

Oakiey said:

I'm not sure about the cmh, it got like 17000 fewer lumens than a 400w HPS

How in the hell is it supposed to replace a real 600 wat light?

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First Lumens are Humans not plants, but that said....

1 315watt CMH they say will replace 600watts HPS, but it doesn't well not footprint wise. They say this as marketing gimmicks because 2 315watt CMH will be able to generally replace 1 1k HPS, and allows for a more even footprint, but a single 315watt CMH most definitely doesn't replace a good 600watt HPS in a good hood. It took me til just this year to finally start phasing out my 600HPS in XXXL magnum hoods. Mostly because finding new magnum hoods was a PIA in 6in for a while.

I am a happy camper though my SF4000, and my MARS SP250s as well as an HLG 550v2. What I learned in the process though is to properly and evenly cover a true 4x4 Botanicare white flood table is it takes about 600watts of power anyway you slice it. LED, HPS, CMH, or even High Output T5s. Now that said YES the HLG and SF's are about 480watts but they leave some footprint dropoff around the edges to be desired.

So far my best results where multiple SP250s over a single table ( 2 works well, 3 kills it! ). I am glad manufactures are going to the Fluence/Synce style bar/strip light designs as they just provide such good even coverage. I am excited to see Mars drop their new FC line soon which looks like a Gavita/Fluence knockoff and uses lm301b's and Osram 660nm reds..... if they deliver on the quality and design I know they can and did on their SP line, if the price point is right I can see them selling TONS!!!

Only time will tell, but hopefully it will give a better budget option for those that want a strip setup without DIY or big $$$$$.

Rocket Soul said:

High end leds are over 50% efficient for a few years now. you can even get 365nm LEDs that are close to 50%: https://www.digikey.es/product-detail/es/new-energy/LST1-01G01-UV01-00/1672-1123-ND/7926550 .

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interesting way outside my budget

Prawn Connery said:

I'm not sure I've seen that graph before. It is quite different to other, more common plant absorption graphs – though this one appears dedicated to cannabis and not other plant species. Where is it from? Is this total absorption of all combined photosynthetic pigments? Ie, Chl-A, B, Carotenoids etc?

This is an old thread, but the study I linked to is from 2012 so is pretty dated. I'm assuming the reason they chose the LED wavelengths they did is because they were the most common/economical/efficient LEDs available at the time. Things have moved on since 2012, but it is still commonly believed that total photons > spectrum, which is why efficiency is still regarded as > than spectrum.

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That graph and some others can be found on icmag. Posted by someone called Beta Test Team. Links for their spreadsheets are dead and gone, but posts were still there a while back.

I personally prefer 3000k for a full cycle light. Still smashes it in the veg department and backs the flowering cycle with a bit of meat compared to a 4000k in flower

wietefras said:

You are confusing absorption with photosynthetic efficiency.

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Yes, you're right. It is a Quantum Efficiency graph, not a pigment absorption graph. Although it does say "Absorptance" at the top, it denotes photosynthetic efficiency of absorbed photons of each spectra – not the same as percentage of photons absorbed.

wietefras said:

Bugbee did some tests and he saw that greens would benefit from more blue in the spectrum (something like 10% more yield). Whereas flowering/fruit bearing plants would yield much better (up to 25% more yield) with less blue in the spectrum. So spectrum does matter indeed.

That PowerVEG light seems to put about half of the SPD in the under 400nm Category. Maybe that confuses things.

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Certainly spectrum matters. Not just in terms of photosynthetic efficiency but photomorphogenic response. My point was simply small increases in light are worth more than small improvements in spectrum, which is the reason why a lot of LED manufacturers prioritise efficiency over spectrum – up to a point.

You seemed to agree with this yourself not that long ago: https://rollitup.org/t/from-des-to-leds.948046/page-10#post-14021543

It's pretty clear most of the photons from that PowerVeg T5 are not being counted by the PAR meter. I pointed that out.

LOL! Here we go again. Alright, I don't want to have another protracted argument with you because this time I actually agree with you and thank you for pointing out it was a QE graph.

mauricem00 said:

if the plant is absorbing the light I assume they are using it for something. UVA helps plants absorb calcium from the soil which may explain the cal-mag deficiency seen with LEDs. the 365nm LEDs I found on amazon have an efficiency of 4.5% (1200mw input 55mw output) with an instant start ballast a T5 HO has an efficiency of 30% even in the UV range.high end LEDs have an efficiency of 40% the new 301 can achieve 50% with 4000k to 5000k and 46% with 3000k or 43.7% with a meanwell driver high quality LEDs are outside my budget T5s are cheap and effective.for a large scale grow I would use CMH

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You might be on to something. I've been testing a new spectrum for Grow Lights Australia which has a bit more UVA and near-UV in it and was surprised how well the plants vegged. In fact, they appeared to veg much faster and healthier than the 5000K Samsung strips I used to veg under that have no near-UV or UVA. These plants were growing in the middle of winter, too, when overnight temperatures got down to around 5-10C and daytime temps were 15-20C with high humidity in the grow area, so VPD was low. There's also a bit of extra far red in there which seemed to have a nice effect on leaf size.

Oakiey said:

Heck for veg I wouldn't even put anything lower than 5000k over a fish tank.

I've got a brand new 400,w 4000k bulb in a drawer, I swear my plants just almost shutdown underneath it...

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The plants in the above photo are under a 2500K light. There are different ways to achieve the same CCT, so overall colour temperature is not always the best way to choose a light.

Prawn Connery said:

You might be on to something. I've been testing a new spectrum for Grow Lights Australia which has a bit more UVA and near-UV in it and was surprised how well the plants vegged. In fact, they appeared to veg much faster and healthier than the 5000K Samsung strips I used to veg under that have no near-UV or UVA. These plants were growing in the middle of winter, too, when overnight temperatures got down to around 5-10C and daytime temps were 15-20C with high humidity in the grow area, so VPD was low. There's also a bit of extra far red in there which seemed to have a nice effect on leaf size.

View attachment 4646203

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Very good. First time I see proof of a 10-15 degree night/day temp difference effect on growth.

mauricem00 said:

if the plant is absorbing the light I assume they are using it for something.

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If it's not (fully) used it simply warms the plant up.

Absorptance and photosynthetic efficiency are different metrics. Both charts were posted in that thread. The Absorptance chart was posted already earlier and this is the RQE chart (adjusted for absorptance) for Cannabis that was presented:

rob333 said:

no not at all did you "If you're vegging for one week and flowering for eight, use the light that's best for flowering - 3000K. In fact, 3000K will veg faster than 4000K too. Lots of scientific studies have shown that added red (around 620nm) promotes faster growth and higher leaf mass in veg as well as flowering" mate if i wanted to watch a guy grow shitty plants with leds i will go to grasscity thanks

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You are such a hater bro, buy some fucking shades and relax n stop trash talking with your uneducated and down right ignorant replies... wheres your hps grow bro? Hows the foxtailing going under your outdated hps tech? Where is your side by side proof that hps is undeniably better and more efficient then the newest LED tech lol. Go to Grassity lol there is more room there for you to talk trash and troll the led forum like a tool bag because you are so single minded and stubborn you wont even aknowledge factual, studied, and proven information. How many anti-led guys are out there trolling the led forums just to hate? You guys got a group i can join and trash talk your shitty hps hot boxes that are less bang for way more bucks and less safe and less reliable and less basically everywhere an led is more. Good luck with your hps grows and the foxtailing you are going to try n curb with nutes and co2 instead of stop heat stressing the hell out of your plants... your posts are like an infectous festering wound on the threads, go away lol we have heard you and aknowledge that you wont listen to science, us, or anyone else besides yourself and wont ever go LED, seriously rob333 we get it bra.

Gardenator said:

You are such a hater bro, buy some fucking shades and relax n stop trash talking with your uneducated and down right ignorant replies... wheres your hps grow bro? Hows the foxtailing going under your outdated hps tech? Where is your side by side proof that hps is undeniably better and more efficient then the newest LED tech lol. Go to Grassity lol there is more room there for you to talk trash and troll the led forum like a tool bag because you are so single minded and stubborn you wont even aknowledge factual, studied, and proven information. How many anti-led guys are out there trolling the led forums just to hate? You guys got a group i can join and trash talk your shitty hps hot boxes that are less bang for way more bucks and less safe and less reliable and less basically everywhere an led is more. Good luck with your hps grows and the foxtailing you are going to try n curb with nutes and co2 instead of stop heat stressing the hell out of your plants... your posts are like an infectous festering wound on the threads, go away lol we have heard you and aknowledge that you wont listen to science, us, or anyone else besides yourself and wont ever go LED, seriously rob333 we get it bra.

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LOL. Back in the day Rob had a real problem with leds but he came to turns with reality and learned to love the LED. His last grows are all led and quite good looking, we all had a bit of fun with all his led trolling history when he finally got it.

A fair amount of Cannabis has been raised quite nicely under 4000+k Metal Halide before the rise of HPS.

Yes, that's what I used when I first started growing. I also mixed it with HPS.

I don’t believe my flowering k rating average of Lights in tent has been under 3500k in 7 or more years.

After reading this thread I'm feeling pretty good about my decision to go with 4000K in my veg tent and 3000K in my flowering tent.
Got a brand new Kingbrite 480W in my 4x4 veg and some new Geek Beast Pros in the 4x8. My first few cycles were disappointing with these Amazon COB LEDs that I've got. I'm excited to see what these new ones will do.

Prawn Connery said:

I'm not sure I've seen that graph before. It is quite different to other, more common plant absorption graphs – though this one appears dedicated to cannabis and not other plant species. Where is it from? Is this total absorption of all combined photosynthetic pigments? Ie, Chl-A, B, Carotenoids etc?

This is an old thread, but the study I linked to is from 2012 so is pretty dated. I'm assuming the reason they chose the LED wavelengths they did is because they were the most common/economical/efficient LEDs available at the time. Things have moved on since 2012, but it is still commonly believed that total photons > spectrum, which is why efficiency is still regarded as > than spectrum.

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many studies use LEDs because they are a cheap and easy way to produce monochromatic light. the in leave action spectrum is very similar to the graph I posted with a little less absoption in the uv range so not all the uv absorbed is used to convert CO2 into sugar.(photosynthesis) some of the energy is used for other plant functions. UV helps plants absorb cal mag and boost the plants immune functions. we still have a lot to learn about our plants

Oakiey said:

I'm not sure about the cmh, it got like 17000 fewer lumens than a 400w HPS

How in the hell is it supposed to replace a real 600 wat light?

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comparing lumens only works if the same SPD to determine actual output power in the PAR range you need to divde lumens by L.E.R. for HPS LER is 450
for MH it's 320 so a 400 watt MH has the same radiant power as a 400 watt HPShe difference in the way they grow is due to different SPDs

wietefras said:

Bugbee did some tests and he saw that greens would benefit from more blue in the spectrum (something like 10% more yield). Whereas flowering/fruit bearing plants would yield much better (up to 25% more yield) with less blue in the spectrum. So spectrum does matter indeed.

That PowerVEG light seems to put about half of the SPD in the under 400nm Category. Maybe that confuses things.

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I see no uv in that bulb https://www.htgsupply.com/products/agromax-4-foot-t5-pure-par-bulb-2/ perhaps your confusing it with the pure veg plus UV https://www.htgsupply.com/products/agromax-pureveg-plus-uv-t5-bulbs-4-foot/

Rocket Soul said:

High end leds are over 50% efficient for a few years now. you can even get 365nm LEDs that are close to 50%: https://www.digikey.es/product-detail/es/new-energy/LST1-01G01-UV01-00/1672-1123-ND/7926550 .

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using those to add 4% uva would cost almost as much as a 2000watt 301 light not including heatsink ad drivers t5would be more cost effective and provide broad band uv including uvb

mauricem00 said:

t5would be more cost effective and provide broad band uv including uvb

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Honestly, if I decided to add uv to my room, fluorescents would be the most cost-effective choice at this time.
I just don't think you get enough bang for the buck with current uv diodes.

mauricem00 said:

I see no uv in that bulb

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Did you actually watch the video that you posted? They show an SPD with a huge amount of UV.