Lumen A unit of measurement of the total flow of light which is emitted continually from a source. One lumen is equal to the flow of light which is emitted from a very small wax candle.
The common 40 Watt incandescent bulb emits some 400 lm (lumen). So the efficiency of that bulb is 400lm/40Watt= 10 lm/watt. LUX = lm/m2, the intensity of light which falls on a surface. Colour Temperature - measured in degrees Kelvin, the color of a light's output in relationship to the degree of heat applied to produce the specified colour of light. Daylight is measured around 5000 degrees kelvin If we direct all light from our 40 Watt lamp towards a floor area of 1 square meter the intensity of light on that area will be 400 lux, (400 lumen distributed over 1 square meter, 400/1 lm/m2 = 400 lux,) which is a little better than moonlight, but far away from the sunlight intensities we need for growing plants. The sun gives some 50 000 lm/m2 = 50 000 lux at the earth surface on a clear summerday. See the table below.
The 40 Watt incandescent lamp is not only too weak for growing plants, it also has too little blue in its spectrum and is far too inefficient. Fluoroscent tubes and HPS and MH lamps are the better choices.
Cannabis needs 24 hours of strong light for the first 4-6 weeks of vegetative growth. Then it needs 2 months of 12/12 hours of strong light and very dark, to flower and ripen. If they get less than 30000 lux they will still grow vegetatively but slower. And they will flower less, if at all.
Light Requirements of "High Energy" Plants 1000 - 5000 lux Min. necessary for life 10000 - 15000 lux Min. necessary for consistent but sparse growth 20000 - 25000 lux Min. necessary for robust growth 25000 - 30000 lux Max. Efficiency for Sub Tropical varieties 25000 - 50000 lux Max. Efficiency for Equatorial varieties
Plants need 25000-50000 lux too grow fast.
90000 lux Max. Sunlight Intensity on Earth's surface This is too much light, it is not good for the plant.
Plants subject to intensities at this level or greater are at risk of "solarization," whereby photosynthesis is retarded. This can happen at noon on a clear Tropical summer day, especially at high altitudes.
140000 lux Sunlight above atmosphere (Solar Constant)
I hope this helps....
Thanky you Greenman for this info.
