Can anyone help me understand the math/physics of grow lights?

  • Thread starter Progshim
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Answer: Don't worry about it. Pot growers typically focus on all the wrong details. You have to start with nutrition. Absolutely nothing else matters until you get nutrition figured. Then you can throw as much light as you want at the plants. Literally. Every single aspect of growing starts with nutrition. Everyone ignores it. I've not seen an off the shelf fertilizer or soil recipe yet that let's you take advantage of high light intensity. Grab any high end grow light. Grab the best bottled ferts. Try running the light at full power. Your plants will get purple stems. The tips will turn white. The yields and quality will suffer. The solution is not to come up with some arbitrary light intensity target, the answer is to fix the crappy nutrition. There's more to it than Nitrogen EC and CalMag, and none of it is arbitrary or subjective.

I promise you, the guys who hone in on the mountain of acronyms in pot growing and ignore the basics of nutrition are not growing amazing weed. They all dim the lights hanging out nutrient deficient plants. Light burn and heat burn are not a thing with Cannabis. Purple stems is not protecting the plant from light, it's begging for proper nutrition. There's much more to fertilizer. It's straight crackhead activity to worry about light science after paying for pre-built lights. The people who build the lights are the only ones who need to worry about all that shit. You don't need to be a freaking light engineer to grow pot.

Does every single person who drives a car need to know how gasoline is refined? The aerodynamics of their hood? The composition of their tires? No. Only top fuel drag race crews need to know how to know that shit, and no where near the depth of the manufacturers. And I promise you are not at that level in pot growing if you completely ignore the science of nutrients as almost all pot growers do. I see it every day, "light burn, turn the dimmer down" when all it is, is nutrient deficiency causing light sensitive as a side effect.

Learn nutes, pot growers. First and foremost. I've grown my entire life, started outdoors, no dimmer knob. The idea that people need to regulate indoor lighting is absurd.
I am brand new at home growing, and it has changed my life. I have changed my office into a grow room and spend my days with the plants, fish, and cats. There is so much the plants themselves can teach us. I am growing a photo and an auto together as a learning experience. God is in the details, and the Devil listens too. :-)


Most people here are taking their information from a man named Bruce Bugbee.
Here's a video of his on far red lighting. It goes over some of the basic technical aspects and I'm sure you can find content of his more catered to your inquiries... or at least as a jumping off point.
I guess I was wrong. I didn't already know this about far red wavelengths. It's interesting too, thank you


There are many ways to grow for sure. Successfully. But this understanding the nuances of this plant and steering it to your desire is also a worthwhile study to some. I'll give you an example - in another thread I am influencing IBL Durban Poison to be short with blue photons. They look like indica right now, but have a way to go. For some of us, this is fun. I don't grow to sell, I do it for the puzzle. It's a hobby. If somebody else wants to join the hobby, learning about lighting is a great first step. Just the tip of the iceberg tho.
I too am a hobbiest above all, while i do try to allow tthe hobby to pay for future research it is more about the love of growing, not just 420, but everything, that drives me. I grow mushrooms, fruits and vegetables, and herbs everything from fungus to trees, and understanding sunlight's role in photosynthesis is a key element to growing anything for sure. I also grow bees, dogs, rabbits, children, grandhchildren and sometimes myself.


Depends on light, a full spec light has all the colors of the sun mostly red and ir, a 2 cycle light can be made to run full spec but also blue and green witch autos luv, a 2 cycle light can also be turned into a bloom light mostly red, the par is how far the light spreads out.

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