Stop spreading FUD. You do not HAVE to run lenses or reflectors to be effective at all. Many of us do not run any optics and do well. I am going to have to wait about 2 weeks before I know my total for this time around but my past 2 LED grows have resulted in good yields and neither were optimal with room for improvement. Hoping I made the changes needed this time around. Considering I am yielding just a little less than CoralMafia and he is running much better efficiency (more PAR/w), Id say that bare cobs are far from useless. I usually run 12-16" without issues.
Yield from COB's
- Thread starter Safehaven
- Start date
Hybridway
Well-Known Member
The best lessons are those hard learned for me. You'll get it bud. For me cleanliness is key. But not even that is 100%. Pre-treatment too. Good loli-popping goes along way too. Box fans under the canopy help keep air moving too.
Nice light set-up though. You'll do well w/ it once you get dialed in.
Get rid of the clones that have the PM. It will most likely come back even if you rid it now.
I just took 25 or so new strains & found pm on a few. To the garbage they go. Sucks but it will suck allot more if it comes back wk 4 of flower, that's for sure.
Good luck!
Hybridway
Well-Known Member
Not saying useless by any means. Just allot less effective w/ light spraying everywhere. Dropped to 10"-14" should be helpful. You'll get a much higher PPFD & still have the required footprint.
I'm about to drop mine down cuz I don't have the height for the lenses. But I have 90• reflectors. Still no where near as bright a canopy as the other light w/ lens & I'm at around 18" while the lenses light is around 28"-32".
Hybridway
Well-Known Member
Using lenses gives you a waaaayyy brighter canopy.
I just added lenses to my new light w/ CXB 3590's running @ 100w each. Freaking crazy bright.
wietefras
Well-Known Member
In fact as Malocan demonstrated in his 4'x4' test, when both placed at the correct height, the COBs with reflector averaged 20% less light than the ones without.
But indeed, the bare COBs need to be at about half the distance of their reflector bearing colleagues.
Same goes for lenses. They will only lose light. Perhaps a little less than reflectors but still.
But indeed, the bare COBs need to be at about half the distance of their reflector bearing colleagues.
Same goes for lenses. They will only lose light. Perhaps a little less than reflectors but still.
Hybridway
Well-Known Member
I highly disagree. You're focusing light to your plants rather then wasting it.
What good is more total light if 1/2 of it isn't hitting your plants?
I'll take a total light loss to get 80% light gain on my plants any day.
I'm using reflectors coupled w/ lenses & the light hitting just the canopy is outta this world bright.
The only thing brighter is my white ass.
Focus your light. There's a reason the PPFD readings are substantially higher using lenses.
wietefras
Well-Known Member
You can disagree all you want, but the evidence is quite clear. Malocan tested this and on average he measured a 20% difference over the whole grow area in favor of bare COBs. It's pointless discussing this when it's a proven fact. Although I think he put the reflector fixture too high at 60cm, but even when lowered by maybe 10cm that's going to increase the average PPFD by a few percent at best.
The lights are supposed to positioned at the height above the canopy where you get best uniformity. When you focus the light with a lens or reflector, you simply need to hang the lights higher to get the same uniformity. Which actually results in more wall losses plus reflector/lens losses to boot.
Tests that prove there is more light straight under the COBs are meaningless. Of course there is since the light is compressed in a smaller area, but that just means there is less light somewhere else. Minus the reflector losses.
The lights are supposed to positioned at the height above the canopy where you get best uniformity. When you focus the light with a lens or reflector, you simply need to hang the lights higher to get the same uniformity. Which actually results in more wall losses plus reflector/lens losses to boot.
Tests that prove there is more light straight under the COBs are meaningless. Of course there is since the light is compressed in a smaller area, but that just means there is less light somewhere else. Minus the reflector losses.
Airwalker16
Well-Known Member
I'll stick with my angelinas. 
Hybridway
Well-Known Member
More data hu!
Have you grown w/ bare, reflector, & lens?
When you do, you'll better understand.
I agree w/ you if you agree that bare cobs should be dropped low to the plant.
Either way, lenses produce a much higher PPFD in an area covered w/ suitable growing intensity
wietefras
Well-Known Member
I understand that it's hard to grasp when you see a higher PPFD right under the COBs, but those higher numbers simply mean you lose the light somewhere else. Plus that you lose around 6% on the lenses or reflectors. Then you need to increase the height with reflectors and lenses and you lose more on the walls.
This not some theoretical debate. Over a 4'x4' area, Malocan measured an average PPFD of 629 under COBs with reflectors and 744 average with bare COBs. The bare COBs only performed worse in the front 10cm where the door was open during measurement. Corrected for that it's even 637 PPFD for reflectors and 764 PPFD for bare COBs.
But you can believe whatever you want. I just wanted to point out that it;s just a belief and that facts say otherwise. I'll leave it at this. No point in debating facts.
This not some theoretical debate. Over a 4'x4' area, Malocan measured an average PPFD of 629 under COBs with reflectors and 744 average with bare COBs. The bare COBs only performed worse in the front 10cm where the door was open during measurement. Corrected for that it's even 637 PPFD for reflectors and 764 PPFD for bare COBs.
But you can believe whatever you want. I just wanted to point out that it;s just a belief and that facts say otherwise. I'll leave it at this. No point in debating facts.
Hybridway
Well-Known Member
So
Until you put some reflectors on & look at your canopy I guess all you have is data to go by. I prefer real life experience myself.
What are your yields like using bare cobs?
How close do you keep your fixture?
I agree w/ using bare cobs @ 8" or so. Deffinetly, riding low w/ a super wide & evenly spread fixture, bare cobs are beneficial.
Yeah, I hear you. You are right.
Until you put some reflectors on & look at your canopy I guess all you have is data to go by. I prefer real life experience myself.
What are your yields like using bare cobs?
How close do you keep your fixture?
I agree w/ using bare cobs @ 8" or so. Deffinetly, riding low w/ a super wide & evenly spread fixture, bare cobs are beneficial.
wietefras
Well-Known Member
Check Malocan's thread. He had the bare COBs at 12" and reflector COBs at 24". At those heights uniformity was comparable. Personally I put the bare COBs at 10" and then the reflectors should be at 19" (correcting height from 115 degree beam angle to 90 degree)
I understand physics and the data matches that. So I don't need to test it to understand that it's not working. Unless you insist on hanging the COBs higher. When Malocan moved the bare COBs to 24" there was a tiny advantage for the reflectors.
Yields are difficult to compare but I get around 0.7g/PPF
I understand physics and the data matches that. So I don't need to test it to understand that it's not working. Unless you insist on hanging the COBs higher. When Malocan moved the bare COBs to 24" there was a tiny advantage for the reflectors.
Yields are difficult to compare but I get around 0.7g/PPF
CoralMafia
Well-Known Member
Sorry for late reply but i veg for around 4-6 weeks usually and i also think the cobs with lenses looks brighter than without but just my opinion i have no data collected.
PhotonFUD
Well-Known Member
Target for ~400umoles as uniform as possible.
Going over and the additional light will do more of:
1. reflect (directly off the surface)
2. transverse (lower wavelengths usually do)
3. change to heat (surfaces and within the plant)
4. and even retransmitted via luminescence by chlorophyll
It is better to hit more plant area with what they can handle than bombarding one area with too much.
Don't just measure PAR but also look at leaf temperature. Higher leaf temperatures are also the result of waste energy from plant functions. Balancing spectrum, intensity, temperature and uniformity is so much fun.
Going over and the additional light will do more of:
1. reflect (directly off the surface)
2. transverse (lower wavelengths usually do)
3. change to heat (surfaces and within the plant)
4. and even retransmitted via luminescence by chlorophyll
It is better to hit more plant area with what they can handle than bombarding one area with too much.
Don't just measure PAR but also look at leaf temperature. Higher leaf temperatures are also the result of waste energy from plant functions. Balancing spectrum, intensity, temperature and uniformity is so much fun.
Greengenes707
Well-Known Member
Do you have any examples(actual grows) of this strategy being successful?
PhotonFUD
Well-Known Member
Sunlight is probably the best example of uniformity in action.
Greengenes707
Well-Known Member
So that is a complete no...why not just say you don't.
Sunlight is not an example of 400umols uniform dude. Try 1700-2000 of uniformity. The sun is up to over 1500umols by 9am and stays that way until damn near sunset(past 6pm) . 9 hours of intense light for a DLI over 40mols...closer to 50mols.
So again...do you have any examples of the strategy(400umols) you are pushing? Ideally from your own work too and with cannabis. But will take anything to start.
wietefras
Well-Known Member
That depends on if you are bound for space or not. I go for 800umol and harvest almost twice as much per m2. Slightly lower g/W perhaps, but much higher g/m2 and also much less work per m2 or per yield.
I have a plant temperature camera in my grow room and I know it's nonsense that plants would heat up on their own. They cool themselves through evaporation. The plants are between 2 and 6 degrees C cooler than the surrounding environment. Even with the lights out (and evaporation is minimal) they are 1C below ambient.
The reason to monitor plant temperature is not to check "internal combustion", but to to compute the Vapour Pressure Deficit (VPD) by combining leaf temperature, ambient temperature and the ambient humidty level. This determines if the plants evaporate too much (might induce rot) or not enough (plants are drying out or overheating).
:edit: Example of the VPD data (orange), plant temperature (green) etc:
PhotonFUD
Well-Known Member
Well there is documented research regarding light absorption for photosynthesis. The text I am most familiar with is 'Photosynthesis' by Hal, Rao published by Cambridge University Press.
Some people are looking for ideas to improve, some aren't as they are completely happy with their current system. I am only referencing publicly available research for ideas that are relevant to the discussion and stimulate some thinking. Useful information comes from many sources. For example, this is a great reference paper for the leaf temperature discussion and even mentions photosynthetic capacity:
http://publish.uwo.ca/~dway4/files/Way and Yamori 2013.pdf
Sunlight is capable of well over 2000 umoles of radiant power. Of that, roughly 1/5 (~400 umoles) of that is usable PAR spectrum absorbed by plants. That is what a number of plant specialists (eg. various biologists, botanists, etc) have come to generally accept, as for example, in the aforementioned university text. The plant can handle more light up to a point where the plant's thermal management fails and damage occurs, however it just won't increase photosynthetic rate.
I used sunlight as an example for the principle benefit of uniformity. At the earth's surface sunlight is uniform to exposed leaves throughout the plant. Radiant power from artificial light drops significantly over distance and benefits from uniformity by help putting light where it can best be used by the plant thus improving efficiency.
My point is that uniformity is important, probably more important than people are investing in.
Also, the optimal radiant power might not be 400 umoles, it could be 600, or even 350 but it is some number and once it is figured out that should be the target for all exposed leaf area.
(edit) yield/area is what you should be looking at, at least that is what traditional agriculture is concerned with.
Yodaweed
Well-Known Member
Sounds like you might got some environmental issues if you getting PM like that. Try more airflow