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

• None

#### Progshim

There is probably already a thread that lays it all out, maybe a sticky. If you know of one, please point me to it. If not;

No offense, but please, I'm not asking for opinions right now. Just the math and measurements.
I understand wavelengths, and why some are more effective than others. Let's leave that part out unless the wavelength affects the intensity.

What I don't understand is how light intensity is calculated. Umol, mol/s, jmol, PAR, PPFD, no idea what any of them are, or how we know their values.
Could someone teach me how to measure and calculate how much light my fixtures are providing? Or do I need to take a class in order to learn this?

No doubt manufacturers like to exaggerate the performance of their lights. Is there a way to find the actual output of my LED lights? I have a cheap tool that measures 3 things, including light intensity, but it only has numbers from 0 to 2000 and no explanation of what they mean.

I'm fine with basic math and some algebra, no calculus.

I'll check back on this thread every few hours. If you can teach me this, feel free to message me instead of posting it here, if you like.

Thank you everyone

#### steamroller

No math needed.
Some use meters to read par[\$\$\$]. Apogee are the industry standard and leader IMO.
I use photone and pay attention to my plants.
Meter won't tell you much more then the plant if you listen.

#### beluga

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.

#### Moe.Red

There is probably already a thread that lays it all out, maybe a sticky. If you know of one, please point me to it. If not;

No offense, but please, I'm not asking for opinions right now. Just the math and measurements.
I understand wavelengths, and why some are more effective than others. Let's leave that part out unless the wavelength affects the intensity.

What I don't understand is how light intensity is calculated. Umol, mol/s, jmol, PAR, PPFD, no idea what any of them are, or how we know their values.
Could someone teach me how to measure and calculate how much light my fixtures are providing? Or do I need to take a class in order to learn this?

No doubt manufacturers like to exaggerate the performance of their lights. Is there a way to find the actual output of my LED lights? I have a cheap tool that measures 3 things, including light intensity, but it only has numbers from 0 to 2000 and no explanation of what they mean.

I'm fine with basic math and some algebra, no calculus.

I'll check back on this thread every few hours. If you can teach me this, feel free to message me instead of posting it here, if you like.

Thank you everyone
What are PAR, PPF and PPFD, and why should you care?

## As a grower, you have a lot of things to care about. Plant lifecycles, grow light positioning, heat, light spectrum, space and market are all incredibly important factors to consider when building a greenhouse or grow area.​

As you explore this world and unpack the different metrics and grow lights and systems that you need for optimum yields and healthy, flavoursome plants, you will hit a wall of acronyms. These acronyms – PAR, PPF, PPFD – sit alongside terms like watts, lumens, photon efficiency and LUX, and they are all critical to helping you create the perfect grow space and yield.
This isn’t as complicated as it sounds. In this guide, we explain exactly what PAR, PPF and PPFD mean, and exactly why you should care…

## What is PAR (Photosynthetic Active Radiation)?​

PAR stands for photosynthetic active radiation and describes the wavelengths of light that sit within the visible range of 400-700nm. It was originally defined by research undertaken by Dr Keith McCree in the early 1970s, and it is described as the type of light required for photosynthesis. PAR doesn’t measure light, it is rather a term that can help the grower determine the type and volume of light that’s needed to optimise plant yields and health. PAR light is leveraged by grow light systems to mimic natural light and can be optimised with other light solutions to change light density, usage, and measurements.
For the grower, PAR is a term that should be used to help fully realise optimal lighting layout and usage. It is also an important consideration when purchasing grow lights – ensure that you fully understand how much PAR they produce, how much energy they use to produce their PAR, and how much PAR is available for the plants. These are some of the basic considerations that need to be managed before you sign on that dotted line.

## What is PPF (Photosynthetic Photon Flux)?​

PPF is the term used to define the measurement of PAR. It stands for photosynthetic photon flux and its value determines how much PAR is being produced by any one lighting system over the period of a second. PPF is the second essential ingredient in your recipe to the perfect lighting for your grow space. This is what helps you to establish exactly how much of the light your grow lighting system is producing can be used by your plants for photosynthesis.
For the grower, measuring PPF requires equal parts understanding of the process and mathematical patience. There are PPF measurement tools available on the market, but you can work with a trusted partner who can help you create a lighting system that’s efficient enough to deliver the PAR and PPF you need. PPF is measured in micromoles per second (µMol/S) – one micromole is around 602 quadrillion photons (source: LED Gardener)

## What is PPFD (Photosynthetic Photon Flux Density)?​

The third part of the PAR equation is PPFD. This stands for photosynthetic photon flux density and it does more than just measure the PPF, it also measures the surface area. PPFD is measured in micromoles per square metre per second (µMol/m2/S) which establishes exactly how many PAR photons are landing on a specific area. PPFD is all about how many of those essential, photosynthetic photons are actually impacting the grow area and how well those lights are working when it comes to their output.
For the grower, it’s important to make sure that the PPFD data you get from your grow light manufacturer is accurate and covers the entire area of the light. It’s relatively easy to massage this information, so consider factors such as distance from the light source, a number of measurements that account for the average, and the minimum/maximum ratio before you buy. This is another great reason why you should work with a trusted grow light partner who can offer you relevant metrics and the right tools to fully benefit from PAR, PPF, and PPFD.

#### BigBlonde

It's important to understand that the growth stage and the health of the plant matter when considering how much light (and nutrition) the plant needs and can put to use.

#### strider26554

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.
Man, I couldnt have put it any better myself, im 56 years old and ive been growing since my late teens, theres nothing you can pull out of the sun without the right dirt, and theres nothing the sun wont give you with the right dirt. I see people on here discussing lighting as if it is the key to being a good grower,, but we , the old-timers that is, know that its the dirt, My advise to new growers is to grow in soil first,,

#### beluga

It takes many tools to build a house.

I don't think OP is disregarding all of the other aspects of growing; they just seem to be looking to expand their knowledge of a very critical one.

#### Moe.Red

Man, I couldnt have put it any better myself, im 56 years old and ive been growing since my late teens, theres nothing you can pull out of the sun without the right dirt, and theres nothing the sun wont give you with the right dirt. I see people on here discussing lighting as if it is the key to being a good grower,, but we , the old-timers that is, know that its the dirt, My advise to new growers is to grow in soil first,,
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.

#### growsince79

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.
Are you going to share your secret recipe?

#### growsince79

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'm also experimenting with spectrum and hi/low light spikes -cool stuff.

#### Progshim

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.
Thanks!

#### Progshim

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.
Thanks but I'm not looking for opinions. Peace

#### Progshim

What are PAR, PPF and PPFD, and why should you care?

## As a grower, you have a lot of things to care about. Plant lifecycles, grow light positioning, heat, light spectrum, space and market are all incredibly important factors to consider when building a greenhouse or grow area.​

As you explore this world and unpack the different metrics and grow lights and systems that you need for optimum yields and healthy, flavoursome plants, you will hit a wall of acronyms. These acronyms – PAR, PPF, PPFD – sit alongside terms like watts, lumens, photon efficiency and LUX, and they are all critical to helping you create the perfect grow space and yield.
This isn’t as complicated as it sounds. In this guide, we explain exactly what PAR, PPF and PPFD mean, and exactly why you should care…

## What is PAR (Photosynthetic Active Radiation)?​

PAR stands for photosynthetic active radiation and describes the wavelengths of light that sit within the visible range of 400-700nm. It was originally defined by research undertaken by Dr Keith McCree in the early 1970s, and it is described as the type of light required for photosynthesis. PAR doesn’t measure light, it is rather a term that can help the grower determine the type and volume of light that’s needed to optimise plant yields and health. PAR light is leveraged by grow light systems to mimic natural light and can be optimised with other light solutions to change light density, usage, and measurements.
For the grower, PAR is a term that should be used to help fully realise optimal lighting layout and usage. It is also an important consideration when purchasing grow lights – ensure that you fully understand how much PAR they produce, how much energy they use to produce their PAR, and how much PAR is available for the plants. These are some of the basic considerations that need to be managed before you sign on that dotted line.

## What is PPF (Photosynthetic Photon Flux)?​

PPF is the term used to define the measurement of PAR. It stands for photosynthetic photon flux and its value determines how much PAR is being produced by any one lighting system over the period of a second. PPF is the second essential ingredient in your recipe to the perfect lighting for your grow space. This is what helps you to establish exactly how much of the light your grow lighting system is producing can be used by your plants for photosynthesis.
For the grower, measuring PPF requires equal parts understanding of the process and mathematical patience. There are PPF measurement tools available on the market, but you can work with a trusted partner who can help you create a lighting system that’s efficient enough to deliver the PAR and PPF you need. PPF is measured in micromoles per second (µMol/S) – one micromole is around 602 quadrillion photons (source: LED Gardener)

## What is PPFD (Photosynthetic Photon Flux Density)?​

The third part of the PAR equation is PPFD. This stands for photosynthetic photon flux density and it does more than just measure the PPF, it also measures the surface area. PPFD is measured in micromoles per square metre per second (µMol/m2/S) which establishes exactly how many PAR photons are landing on a specific area. PPFD is all about how many of those essential, photosynthetic photons are actually impacting the grow area and how well those lights are working when it comes to their output.
For the grower, it’s important to make sure that the PPFD data you get from your grow light manufacturer is accurate and covers the entire area of the light. It’s relatively easy to massage this information, so consider factors such as distance from the light source, a number of measurements that account for the average, and the minimum/maximum ratio before you buy. This is another great reason why you should work with a trusted grow light partner who can offer you relevant metrics and the right tools to fully benefit from PAR, PPF, and PPFD.
I've only glanced at this because I don't have time just yet, but it looks like exactly what I wanted. Thank you !!!

#### Progshim

It takes many tools to build a house.

I don't think OP is disregarding all of the other aspects of growing; they just seem to be looking to expand their knowledge of a very critical one.

There are a great many things that I can learn from the HUGE amount of information held by the people on this forum.

Right now I want to understand light intensity and I want to know what it means when I see one of those specs....PAR, PPFD, etc.

Thank you for understanding.

#### Progshim

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.
Exactly. It's a hobby for me too. I don't even smoke, and I give away most of what I grow.

And knowing how things work ROCKS

#### BehindEnemyLines

Are you going to share your secret recipe?

“You can throw as much light as you want… Literally”

#### Progshim

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.
Thanks but I'm not looking for opinions. Peace
This was dismissive of me. Let me answer properly.

I have no doubt that correct nutrients are important, that would be true for any living thing. And it sounds like you're pretty savvy in that department. That's great and thank you for being willing to share. Right now I'm not looking for that info but I love that when I AM looking for it, there are people like you that can and will help me.

Do I NEED to understand lighting? Nope but I want to. Light intensity doesn't only affect pot plants, it also affects human skin, and how quickly house paint fades. I'm not a dermatologist or a house painter either. I like learning the nuts and bolts of things sometimes.

Did you know that wattage isn't a measure of lighting? It's got nothing to do with lighting. It's a measure of electricity consumption. Amps x Volts = Watts. We use wattage to describe the brightness of lights only because for a long time incandescent bulbs were all that was available to the average consumer, and it was convenient for lightbulb manufacturers. Personally, I find that fascinating.

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#### Progshim

No math needed.
Some use meters to read par[\$\$\$]. Apogee are the industry standard and leader IMO.