Rahz
Well-Known Member
He said he's growing in a 2x4. 550 PPF in a 2x4 is 735 PPFD.
Olive Drab Green
Well-Known Member
Rahz. PPFD is measured in micromols per square meter. That is what the number is. What are you talking about?
Yodaweed
Well-Known Member
So that's half what a 600w hps covers. And similar PAR ratings , his 271 watts is approx half a 600w hps, or 300w of HID light sounds about right. Mono's are still king for lumen/watt , look how much lumen per watt those samsung quantum boards make but their intensity sucks.
Olive Drab Green
Well-Known Member
Optimal PPFD by your own site's assertion is 800-1200. Each light puts out at least 830 in an 18x18. One puts out 932 in an 18x18, again, by your site. I have three lights in a smaller area than ( 18x18 ) x 3, meaning density is further condensed.
Rahz
Well-Known Member
Okay, I though you were growing in a 2x4 for some reason. If your area is smaller than 18x18x3 then the PPFD will be higher than 830.
Olive Drab Green
Well-Known Member
18x18x3 is 4.5x4.5. 4x2 is smaller.
Olive Drab Green
Well-Known Member
18 is 1.5 feet. Times 3 is 4.5.
wietefras
Well-Known Member
PPFD is a spot measurement like lux. PPF is a total light output like lumen. You cannot compare the two.
As Rahz explained, the PPF for 241W would be 550umol/s. That's half of what a 600W HPS would do (although you'd need to subtract some reflector losses).
Of course when you use that 241W fixture to light half the space of the HPS producing twice the amount of light, you would get the same PPFD. That doesn't say it produces the same amount of light.
Rahz
Well-Known Member
Yes, umol/m/s is the PPFD the way you said it was redundant... but probably not the best example for me to bring up. Cobs are just an array of LEDs, nothing special about them in that regard. It's the efficiency that matters. 241w at 2.3 umol/j = 554. 600w at 1.09 umol/j = 654. More than that I think when the discussion get's heated nobody wins.
shadow_moose
Well-Known Member
I see you saying this all over, but do you have any proof whatsoever? It seems like you spout off about stuff you don't fully understand all too often.
I just got a quantum board two days ago and "intensity" is marginally superior to comparable COBs. I've done some basic PAR testing (far from complete) that indicates this. I'm sure intensity would be just as good at distance if I had gotten some lenses to go on it, but I don't currently have access to lenses. I think @robincnn is getting some lenses for the quantum boards. When we get those available, I have no doubt these boards will outperform most COB rigs people are building. It out does my citis, and I'm waiting to test the board against Vero Gen 7's when I get my hands on some.
BuddyColas
Well-Known Member
So class is in session. So the umol/j is a figure that you get from a sphere right? And unless you had a sphere you'd get that from the manufacture. Please explain how you went from umol/j for a light source to PPF to PPFD for a given space. Thanks.
Yodaweed
Well-Known Member
It's basic science, law of square inverse states intensity is directly proportional to the distance of a fixed point object, the initial value of that object is the largest factor on that intensity, when you run diodes that are 1-3w you will have strong par readings at a short intensity but when you go further from that distance the drop off is substantial. Thel larger the value of the fixed point (light) the further you can move the plants away and still have acceptable par, in short a 1000w single point light can be hung 10x higher than a 100w single point light . Those PCB board lights are best for small enclosed grow spaces with restricted height (micro grows). Lenses will push the intensity of the light further but make hot spots and also you lose some light when you use those. LEDs are best run bare for max intensity and close to canopy.
Rahz
Well-Known Member
It's the same basic formula you would use with any light source. The idea that a measurement made by the component manufacturer is the wrong basis for determining the expected light intensity is silly.
The PPFD will be changed based on optics, distance from canopy, reflectivity of the walls, etc. but that is true for any light source. Deriving the PPFD from the PPF is a non-biased approach that will allow someone to compare two light sources. Whether they're 100% accurate isn't the point. If I use the same formula for comparing a HPS lamp then I end up with a reasonable comparison.
The PPFD will be changed based on optics, distance from canopy, reflectivity of the walls, etc. but that is true for any light source. Deriving the PPFD from the PPF is a non-biased approach that will allow someone to compare two light sources. Whether they're 100% accurate isn't the point. If I use the same formula for comparing a HPS lamp then I end up with a reasonable comparison.
Rahz
Well-Known Member
How much higher can a 1000w single point light source be hung compared to a 1000w lamp with multiple sources?
Yodaweed
Well-Known Member
A single point could be hung higher than a 1000w mutli diode fixture, that's why it's suggested you hang a large COB fixture 12-18 inches whereas you hang a 1000w DE light 3 ft +.
Yodaweed
Well-Known Member
If you hang a 1000w gavita 18 inches above your plants you would most likely have some dead plants. At the very least they would be bleached from intensity and fade super fast.
shadow_moose
Well-Known Member
That's actually because of heat and the fact that LED's don't produce IR light, it has nothing to do with "intensity".
Yodaweed
Well-Known Member
That is untrue, you can easily bleach plants when HID lights are too close, nothing to do with heat at all.
shadow_moose
Well-Known Member
The bleaching is a result of the IR.
Yodaweed
Well-Known Member
That's untrue again, you can bleach plants under LEDs , its too much intensity....too many noobs on the LED forums here, its sad.