I just got this off the net. it Demonstrates how the intensity of light on a object would decrease if you moved The object away from the light
Light intensity is inversely proportional to the square of the distance. The formula for this is: light intensity ⍺ 1/distance² . If you quarter the distance, the light intensity would be sixteen times greater. and if you quarter the light intensity, the distance would be sixteen times greater.
If you run a small clip on fan directed at the driver for the light it will help keep the driver much cooler. As long as you’re happy with the way you run them and are getting satisfactory results that’s all that really matters.
For me the distance of the leds to the canopy is all about getting the best coverage so that you aren’t getting any hotspots where 1 plant is getting 1000ppfd and the plant right next to it is getting 250ppfd. Light meters are critical for this purpose. Raise the led light high enough off the canopy where you are getting the best light distribution and even coverage then dim up or down to get the PPFD/DLI target you want. keep in mind the higher the ppfd/dli and the more you will need to feed the plant so it can keep up with the high light intensity.
That’s a good tip firstcav fan cooling The lights good I suppose I do something like lazyhippie suggests And yes, as lazy hippie suggests for the plants to benefit from the extra light it’s will need extra food. And it’s good to bear in mind The formula. Which basically states. If you move on object That’s 8 feet away from the light to 2 feet away from the light You will be getting 16 times the light intensity to that you were getting at 8 foot.
I just want to give the big tick to lazyhippies suggestion of the light meter. I think it’s very important, no matter what kind of light you were using and it doesn’t have to be in the expensive one.
Not to thread hijack bit where does one find optimal ppfd for canopy? Is it based on your light? I’m in flower and honestly have no clue what I’m doing. I have lights at top of tent as high as possible running 80% light. Do I want plants closer during flower?
My lights are 120° spread. Most are unless they have a lense or if they are a cob light. Cob light are usually cone shaped cause the light is coming from one source… but that brings up the whole is LED lights a wavelength or particles that rain down on canopy discussion. Lol LEDs are still in there infant stage as far as that goes. In my pictures you can see that it’s like a beaming rainbow which makes me think it’s particals but IDK 
Hi animosity. My suggestion would be to move them fairly close to the top of the canopy. it would be beneficial to have some kind of light meter to take some of the guesswork away.
And I don’t know what lights you are using specifically. If they were bars at 80%, I would feel confident to have them 6 inches from the top of the canopy. But I would urge you to listen to some of the opinions from others
From what I’ve been reading it’s 12-16" veg and 16-30" bloom . 6" in my opinion is too close for the light to blend with the other diodes that makes it full spectrum. Ibut also read that in flower spectrum doesn’t matter the intensity is what matters. Anyone have any thoughts on this one?
less then 40$ for the lux meter and a download of an app to your phone while following the video guide I posted and you will have a ppfd meter thats within 98% accuracy of a $600 apogee meter.
Optimal distance of the LED to the canopy is going to be totally dependent on what light you have. LED bars have a better uniform coverage and are made for vertical farming so they can be dropped pretty low to the canopy where quantum board styles are alittle more focused so they probably need some space.
The guy you want to listen to is Bruce Bugsbee: Here is a good video to start with. He goes over PPFD for cannabis and DLI, DLI is really the more important concept to consider. Think of it as the amount of light photons you are feeding your plant in a 24 hour period. Its the intensity of your light (PPFD) in relation to the number of hours of lights on. Know what DLI you want your plants to have and how long your veg light cycle is and then you can use a dli calculator to figure out what your ppfd needs to be. Cannabis does well with 20-40 DLI with 40 DLI being roughly the equivalent of 1000PPFD for 12 hours of light. if you wanted that same DLI in veg with 18 hours of light you would only need 617PPFD. Once you start pushing 40 or higher DLI is when you need to push nutrients and CO2 enrichment to get the benefits.
I’ve heard this guy talk before
he’s well worth listening to
Very interesting stuff @The_Lazy_Hippie and even though i am not a very theoretical guy, i learn that i need it to improve on my grows.
I am at a point that i discovered that light intensity is more important than watts, but i cannot measure it yet. So i need the DLI meter you mentioned to measure it.
What i want to measure is if i can achieve the same light intensity with my Samsung d.i.y. ledstrip lamp by hanging it lower as when hanging it higher with increased watts. The lamp has the same footprint as my growtent.
So can you achieve the same by dimming with the lamp as close as possible to the canopy as when increasing the watts further away from it?
What are your thoughts about this?
I had a lot of fun playing with my DIY light (it’s about 43" x 44" in a 4’ x 4’)
It’s interesting seeing the effects of the inverse square function in action.
What really caught my attention is how even the light intensity map is with the spread out bar lights. Whether this is important or not depends on your growing style.
If you are SOG/SCROG you will love dimming and getting close.
I tend to have plants at different heights so I’m generally higher and brighter.
Cheers
G
Yes, I’ve had to change the shape of my plants when I changed from HID to LEDs I need a pretty flat canopy The flatter the better. I usually do my tall plants outside in summer
Full spectrum is needed in flower as in veg, its just different ends of the spectrum, cooler in veg and warmer in flower.
You also can open one of the shoots in the top of the tent to vent out the heat and adding a fan that blows up will help dissipate the heat as well. Heat will naturally rise anyway and you will not have the ballast heat problem or move the ballast outside of your tent if you have those types of fixtures.
How much heat does ballast put out? Is it significant?
The heat they put off varies from ballast to ballast, but can be checked with a heat gun.