Lumens - what to remember

I see a lot of people that are having issues with lumens and how to understand them. Here is the best way I can explain it.

A Lumen, is the amount of light given off by ONE candle flame a foot away.

In understanding this, the farther the light source the less the lumens. i.e. a 23w CFL bulb puts out 1700 lumens which is equal to 1700 candle flames a foot away. move that light 2 ft away and now you only have 1/2 the lumens reaching your plants. you lose almost no lumens with cfl's as you should have them 2-3 inches from your plants. now think of hid's, you must keep your 1000w ( 57,000 lumen ) light between 18-24" from the tops of your plants already losing 1/4 - 1/2 the lumens. Which is why reflectors and reflective material are sooooo important. remember that light dissipates as it travels and loses strength each reflection.

If you can understand this, you can successfully grow a good harvest using only cfl's as well as using only an hid.

yaaaaay lumens.
they make my babies happy..

"A: Lumens is an antiquated way of comparing grow lamps. Lumens are a scientific definition based on the human eye and NOT on a plants response curve. This is the hardest part for people considering trying the CMH's to get past. We have been snowed over by the manufacturers just focusing on the max lumens."

Source

Spectrum is where it's at

Green Cross said:

"A: Lumens is an antiquated way of comparing grow lamps. Lumens are a scientific definition based on the human eye and NOT on a plants response curve. This is the hardest part for people considering trying the CMH's to get past. We have been snowed over by the manufacturers just focusing on the max lumens."

Source

Spectrum is where it's at

Click to expand...

you are right. but people often misconcept the idea of lumens with cfl vs hid and in general. spectrum is just the color/temp of the light, lumens is like gasoline for an engine which would be the bulbs kelvin temp.

This is the cfl forum and the best and most simple way to calculate needed light is with lumens because it brings all kinds of bulbs to a common denominator.

Great info!

I have 22,400 lumens in my 3.9583333 sq ft space.

5659 lumens per square foot WOWZA! LOVING it.