good site

KYbudShredder

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scott06

I believ Soc set you straight on this...but just to make sure some quote from this tut on r site
http://www.greenpassion.org/f22/cfl-tutorial-2592/

i agree k and lumen are two different things..

lumens non-technically speaking are how strong or much light...more lumens more powerfully bright

and

k is a meaure of what part of the light spectrum is being produced...you know ROYGBIV..red, orange, yellow, green, blue, Indigo, Violet

but more technically they can be explained in the tut

Lumens
Without getting too scientific, lumens are what make a plant grow. In general, the more lumens shining on the plant the better. Much of what I have read says 1000 to 2000 lumens per square foot for vegging, and 3000 to 5000 lumens per square foot for flowering. In general, most cfls have a lumen/watt ratio, or efficacy, somewhere around 65, but usually between 55 and 75. Smaller cfls general have lower efficacies, and larger cfls have slightly higher efficacies. This is great compared to incandescent bulbs, which average between 8 and 20 lumens/watt. However, it doesn't hold a candle to hps and mh lights, which usually get between 100 and 150 lumens/watt.

So cfls are fairly efficient, but you need multiple cfls working together to grow.

What the heck is color temperature?
Technically, color temperature means the temperature of an ideal black body radiator at which the color of the light source and the black body are identical. (A black body is a theoretical radiator and absorber of energy at all electromagnetic wavelengths.) Thus, for a 2700K light bulb, the blackbody would be 2700 Kelvin, or approximately 4860 degrees Fahrenheit. What does this mean to a grower? A plant in nature is used to different having a cycle of light throughout its life span. Beginning in spring (fall in the southern hemisphere), the plant is subjected to many long days of light at a high temperature, usually between 5000K and 6000K. This light is very white, and somewhat bluish. Later in the plants life, it sees more and more red light, which helps it to know when to flower. The scientific reason for this is that during shorter days, the sun is not directly overhead, and due to the wavelengths of light, more blue light is bounced off the atmosphere than red light. Some people think backwards (helped in part by the producers of cfls, see below), that a red color is hotter than a blue color. If you light your lighter (I'm sure most people reading this have a lighter), you'll notice that the flame is blue at the bottom, where it is warmest, and yellow at the top. The reason you won't see any red is that the gas burns too quickly for the flame to be red. However, the red can be seen in a fire. Note that in the picture below, the top of the list on the right coincides with the bottom of the color scale.


So which bulbs should I get?
For vegetative growth, you will want bulbs which are at the high end of the spectrum (5000K to 6500K). For flowering, you will want bulbs at the low end of the spectrum (2700K to 3500K). Unfortunately, some manufacturers think that the color spectrum is too confusing for people, so they came up with other words to describe the color spectrum of the bulb. The typical incandescent bulb is 2700 Kelvin and produces a "Warm white" or "Soft white" light. At 4000 Kelvin, a "Cool White" fluorescent light is sometimes called "neutral". A "daylight" fluorescent light is rated at 5000 to 6500 Kelvin and provides cool light with a blue tint. Notice that a "cool white" bulb emits light at a hotter temperature than a "warm white" bulb. Confusing, huh? Note that the light temperature does not affect the temperature of the bulb itself. Also, be aware that the phrases used above are not standard. For example, Sylvania "daylight" bulbs are rated at 3500 Kelvin. This confusion will be coming to an end soon, though, since Energy Star 4.0 guidelines will require labeling all cfls with the color temperature.