Color Theory - Why Broad Spectrum Makes Sense

Articles by: William Boune
COLOR THEORY:  Why Full Color Spectrum makes the most sense.

Outdoor Sunlight produces a full but seasonally shifting spectrum of light, during the long summer days when the sun is high overhead the sunlight is of longer duration, greater intensity and contains a higher ratio of Blue light, HID/MH lamps color rendering index does not mimic this season's index closely enough, HID lamps produce excessive Yellow light which is not very useful to growth with harmful UV and IR. levels, about 25% of the energy is useful.  In greenhouses and outdoors, the long lighting period, the intensity and color content all effect the amount of growth experienced during the summer season.

During the late summer and fall as the sun appears to become closer to the horizon, the light passes through the atmosphere at a progressively sharper angle, through thicker air, and is filtered by this lens to have a higher ratio of Red.   But light predominately composed of Red and Blue light is not enough.  Natural sunlight also contains Green but appears predominately white, white light actually contains all visible colors of the natural worlds palette, witnessed by viewing visible light as it is passes through a prism.  Natural light reflects or absorbs as each plant needs and with each season, the colors we see are those which are largely, but not totally, reflected. 

LED and Spectrum: A very good Spectrum can be accomplished with LED light now, if one uses enough different nm range bulbs, I have yet to see truly enough range employed.  To date few manufacturers employ Green, you just can't get a really full spectrum, all of the subtle variations of colors needed without the Green component.  LED's lack the total intensity of Induction Lighting.

Future Applications of Horticultural LED Lighting, Specialized Supplemental Light:  The experts tell me these lights will not be supplemental, but an essential factor.

The Flower Initiator is used for mere minutes after light out as a phytochrome trigger, to hasten the instigation of Budding, reducing the phytochrome switch period from 2 hours to 5 - 10 minutes.