Lumens, Etc.

What is does nm mean in reference to lighting? what does it shand 4? I'm 99.999999% sure it has something to do with the spectrum or color band or watever it's called (inform me on the correct term 4 that 2 please). For example, 400 to 520 nm is where you see violet, blue, and green. which promotes vegetative growth.)

Also, i know almost nothing about lumens. if wat i think i know is right, then it measures the intensity of light. n the more, the better???

please help!
so confused.
:confused::confused::confused:

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Originally Posted by Roughrider

Although I'm still kind of a new poster, I keep seeing a lot of the same comments--many of which are answered an Dr. Khronik's excellent El Cheapo Guide to Lighting. But there are a few things I'd like to add in regard to watts, lumens, cfl, hps, and efficiency and how much light you need. Maybe this should be stickied?

Watts have nothing to do with light or growth. Watts measure how much power a light fixture uses to produce light. You can tell how efficient a light bulb is by looking at watts. A 23 watt CFL produces as much light as a 100 watt incandescent...even though the incandescent has more watts, it's useless. See what I mean?

What you care about is light...more specifically, light energy. That's what plants use during photosynthesis/growth. Light is measured in lumens. In my experience and reading, lumen amounts per sq. ft./sq. m. look like this

2000 lumens sq. ft./21500 lumens sq. m. = Absolute minimum for growth. You won't get much from this, especially after the plant has grown a bit. Not really enough to flower well.

3000 lumens sq. ft./32250 lumens sq. m. = Pretty Good growth. Enough light for the entire light cycle, although your yields may be lower.
4000 lumens sq. ft./43000 lumens sq. m. = Very good growth. Once you pass around 3500, growth rate and ability goes up fast.

Over 5000 lumens sq. ft./53750 lumens sq. m. = Optimal growth. Dense growth in all stages.

Keep in mind that using reflectors, using mylar or having flat white walls, and keeping your lights close to your plants keep you from wasting lumens. It's not just about having light, it's about getting the light to your plants. IMO, people ofter overbuy lights. This creates more light, but the light isn't always hitting the plants. And that creates more heat and ventilation issues, which causes stress problems.

That's why it's still impossible to tell anything about growth or yield based on just lumens. A guy that has an HPS that is too far away from plants that have no walls near them and no ventilation may get poorer results than a grower with CFLs that uses reflectors and has a couple of lights under the canopy in a well-ventilated spot.

HPS lights are often said to generate more heat than CFLs. That's not really true...it's just that they are more efficient at producing light, and there's a smaller surface area on the bulb itself for the resulting heat to dissipate. That means more ventilation. But the higher amount of lumens per watt means you use less power and get greater light penetration through your canopy. Still, I'm a believer that well used CFL's can give you great grows with less ventilation and heat issues. If you're in a small to very small area (less than 4 sq. ft./.25 sq. m.), I'd consider the advantages of CFLs in that way.

But HPS is more efficient. A typical 250 watt HPS bulb/unit will produce about 27,000 lumens. I've seen people use a 250w in a 3' x 3' room and get good results. That's 9 sq. ft. which = 3000 lumens a sq. ft. (Really, a 250w HPS is better in a smaller area.) to give you an idea of the difference in efficiency of CFL vs. HPS, think of this.

23w CFL = 1600 lumens = 69.6 lumens/watt
30w CFL = 2000 lumens = 66.7 lumens/watt
40w CFL = 2600 lumens = 66.3 lumens/watt

compared to

150w HPS = 14000 lumens = 93.3 lumens/watt
250w HPS = 28000 lumens = 112 lumens/watt
400w HPS = 50000 lumens = 125 lumens/watt
600w HPS = 90000 lumens = 150 lumens/watt

So you can see that HPS is more efficient than CFL...and as you get into bigger HPS bulbs, it becomes a lot more efficient. There's also fewer hassles with multiple cords and saved money on your energy bill. If you've got a big area and/or you can deal with the heat and ventilation, HPS is the way to go in flowering. Still, I'm a believer in small HPS lights and combo HPS/CFL grows...if you've got a 2' x 2' room, you can use a 150w HPS and 4 23w CFLs from Wal-Mart and get a terrific grow with very few heat issues.

Hope this helps some people. And, yes, I wrote it all. :)

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Seen a good chunk of views but no reply so i knew i HAD to be missin sumthin.
Thanks goes out 2 roughrider 4 the info.
TOTALLY covered lumens for me.
Hope this helps any1 else lookin 4 the same answers.

BUT WAT ABOUT THAT MN MESS?!?!?!?!!!
Still could use sum help.

nm means ....what you see is not what you get....:cool:

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Originally Posted by growbe

A very good post when it comes to comparing CFL to HID in terms of Lumens and such but, plants "see" light differently than human beings do. As a result, lumens, lux or foot-candles should not be used to measure light for plant growth since they are measures used for human visibility. More correct measures for plants are PAR watts, PPF PAR and YPF PAR, although each in itself does not tell the whole story. In addition to quantity of light, considerations of quality are important, since plants use energy in different parts of the spectrum for critical processes.
Plants are sensitive to a similar portion of the spectrum as is the human eye. This portion of the light spectrum is referred to as photo synthetically active radiation or PAR, namely about 400 to 700 nanometers in wavelength. Nevertheless, plant response within this region is very different from that of humans.
The human eye has a peak sensitivity in the yellow-green region, around 550 nanometers. This is the "optic yellow" color used for highly visible signs and objects. Plants, on the other hand, respond more effectively to red light and to blue light, the peak being in the red region at around 630 nanometers.
Red light provides the most efficient food for plants. However, a plant illuminated only with red or orange light will fail to develop sufficient bulk. Leafy growth (vegetative growth) and bulk also require blue light. Many other complex processes are triggered by light required from different regions of the spectrum. The correct portion of the spectrum varies from species to species. However, the quantity of light needed for plant growth and health can be measured, assuming that all portions of the spectrum are adequately covered. Light for plants cannot, however, be measured with the same standards used to measure light for humans.
First, how do we measure light quantity for humans? The obvious way is based on how bright the source appears and how "well" the eye sees under the light. Since the human eye is particularly sensitive to yellow light, more weight is given to the yellow region of the spectrum and the contributions from blue and red light are largely discounted. This is the basis for rating the total amount of light emitted by a source in lumens.
The light emitted from the source is then distributed over the area to be illuminated. The illumination is measured in "lux", a measurement of how many lumens falls on each square meter of surface. An illumination of 1000 lux implies that 1000 lumens are falling on each square meter of surface. Similarly, "foot-candles" is the term for the measure of how many lumens are falling on each square foot of surface.
Clearly, both lumens and lux (or foot-candles) refer specifically to human vision and not to the way plants see light.
How then should the rating for plant lighting be accomplished? There are two basic approaches to develop this rating: measuring energy or counting photons.
PAR Watts for Plants
Watts is an objective measure of energy being used or emitted by a lamp each second. Energy itself is measured in joules, and 1 joule per second is called a watt. A 100 watt incandescent bulb uses up 100 joules of electrical energy every second. How much light energy is it generating? About 6 joules per second or 6 watts, but the efficiency of the lamp is only 6%, a rather dismal number. The rest of the energy is dissipated mainly as heat. Modern discharge lamps like high pressure sodium (HPS) and metal halide convert (typically) 30% to 40% of the electrical energy into light. They are significantly more efficient than incandescent bulbs.
Since plants use energy between 400 and 700 nanometers and light in this region is called Photo synthetically Active Radiation or PAR, we could measure the total amount of energy emitted per second in this region and call it PAR watts. This is an objective measure in contrast to lumens which is a subjective measure since it is based on the response of the subjects (humans). A PAR watt directly indicates how much light energy is available for plants to use in photosynthesis.
The output of a 400 watt incandescent bulb is about 25 watts of light, a 400 watt metal halide bulb emits about 140 watts of light. If PAR is considered to correspond more or less to the visible region, then a 400 watt metal halide lamp provides about 140 watts of PAR. A 400 watt HPS lamps has less PAR, typically 120 to 128 watts, but because the light is yellow it is rated at higher lumens (for the human eye).
Since plant response does "spill out" beyond the 400 nanometer and 700 nanometer boundaries, some researchers refer to the 350 – 750 nanometer region as the PAR region. Using this expanded region will lead to mildly inflated PAR ratings compared to the more conservative approach in this discussion. However, the difference is small.
While HPS and incandescent lamps are fixed in their spectral output, metal halide lamps are available in a broad range of color temperatures and spectral outputs. With this in mind, the discriminating grower can choose a lamp that provides the best spectral output for his specific needs.

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found this one in the same thread as roughrider
dutch i actually seen those thumbnails in the same thread 2. thnx 4 postin em here 2.

but anyway...nanometers is the actual meaning. (so im assuming)
srry 4 makin another thread on the same topic btw.
i kno how annoyin it can be n i will definately look harder in the future.

Just 2 confirm, Kelvin, K, color temp, and spectrum are all the same?

Yep, think that's it, I'd say they all describe where the light is in the rainbow, which parts of the electomagnetic spectrum are produced by that light.

NM. is a measure of wavelength
A nanometer is just what it says; one billionth of a meter.
Google wavelength and all will become clear.

On my grow journal on update number 7 you will see a link to a page which explains the difference between lux and lumen.

Maybe this can help.

LED Grow update no.7, October 20th, 2011 « LED Logger. Journal Review of Pro-Grow 260 Grow Light

take care