Light Intensity Easy Explanation

I'm going to attempt to make this as simple as possible because too few people understand the concept of light intensity. Unfortunately, I'm not going to make any diagrams. Perhaps someone will be willing to make some and put some up using this explanation, but I will not. I'm also going to make up my own unit of light called a "Light Unit" because i am not up for calculating "lux". It is the same exact thing as "lux" only I am using different measurements. Just like kilograms and pounds measure the same thing, i'm going to use "Light Units" instead of "lux"

1ft away receive 16 Light Units 2ft away receive 4 Light Units 4ft away receive 1 Light Units

This shows that an object 2x the distance away receives 1/4th as much light. This is because light intensity decreases by distance squared. An object 4ft away from a light receives 1/16th as much light.

Now, Suppose we have a 600w HPS giving off 16000 lumens. Any plants:

1ft away receive 64 Light Units 2ft away receive 16 Light Units 4ft away receive 4 Light Units 8ft away receive 1 Light Units

This is exactly true... 4x as many lumens = 4x as much lux/"Light Units" for a given distance.

Now, using this shown concept this means any plants under a 150w HPS will receive JUST AS MUCH LIGHT as any plants 2x the distance under a 600w HPS.

at 6 inches those CFLs have the same intensity as a 150w HPS at 6 inches or a 600w HPS at 1ft

at 3 inches those CFLs have the same intensity as a 150w HPS at 3 inches or a 600w HPS at 6 inches

at 1 inch those CFLs have the same intensity as a 150w HPS at 1 inch or a 600w HPS at 2 inches. (This is however impractical for HPS lights unless they are cool-tubed, it is not a problem at all for fluorescents though)

CFLs are capable of providing just as much light to plants(even more in some circumstances) as HED lights because they may be placed so close to the plants. This is why they are excellent for vegging. HOWEVER, their intensity is very low which is why they are horrible for flowering. Their light cannot "stretch" as far as HPS lights. Where as you may get excellent buds up to 4ft away from a HPS (which also means covering a large area), you would have to keep the buds no farther than 2ft from all of the CFLs for the same results.

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The Point

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ALL LIGHTS are capable of creating the same buds. However, the more lumens that a light gives off, the farther away buds of a decent size will grow. This is why CFLs aren't ideal for budding.

10 1500 lumen CFLs can produce the same buds between 6-12 inches away as a 60,000 lumen HPS can produce 1-2ft away.

1-2ft away from 10 1500 lumen CFLs is the same as 2-4ft away from a 60,000 lumen HPS.

In the end, even though CFLs don't have to worry about heat stress... they are still only really capable of producing 2ft deep of buds. That 600w HPS is capable of producing 3ft deep of buds (3 1/2 ft deep if cool-tubed).

So next time you say CFLs suck, keep in mind they are just as capable of producing excellent buds as HED lights, only in smaller quantities because of few bud sites can be placed next to the lights. For Vegging, they are practically ideal because of how close they can be placed to the tops of the plants to prevent stretching.