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Full Spectrum Bulbs

As an alternative to ordinary lighting, full spectrum light bulbs try to match the light output of the sun with the same relative distribution of energy. The result is better contrast, truer colors, and more natural illumination.

Facts to compare when looking at full spectrum light bulbs are:

  • Color temperature - this measures the visible energy distributed over the spectrum as if it were a simple linear scale, expressed in degrees Kelivn or Celsius degrees above absolute zero. The sun overhead at noon measures roughly 5300 Kelvin (depending on the day and place), so look for values within a few hundred degrees of this.
  • Color Rending Index - the CRI indicates how true colors appear under that light up to a perfect value of 100. Office fluorescents rate somewhere in the low 60's. Look for bulbs better than 90, preferably better than 93.
  • Light output - Lumens are the standard measure of light output not watts since watts measure power dissipated, largely as heat. There is a rough correlation between the light that incandescent light bulbs put out and the power they consume, so other lights indicate their equivalence as a convenience for replacing them. A one hundred watt bulb generates about 1750 lumens.
  • Lifetime - this is how long the bulb may be expected to last expressed as hours of service. Obviously, the longer you may use a bulb before it burns out and you have to replace it is better. Balance lifetime with cost and the inconvenience of replacing the bulb.
  • Type - full spectrum bulbs may be found in three technologies:
    • incandescent bulbs are regular light bulbs with an interior coating that filters the wavelengths of light that the burning filament emits at a corresponding cost in light output. These bulbs come in packages like ordinary bulbs, but for a purplish color, they are frequently found in the elongated version used for fish tanks and plant lights. Flood light versions are also available.
    • flourescent bulbs come in the typical long tubes or horseshoe shapes. Fluorescent light bulbs work by capturing the energy from the electrically excited gas inside them in the interior coating of the glass and radiating it as visible light. Full spectrum light bulbs have a somewhat different interior coating to adjust the light that the coating radiates.
    • compact fluorescent bulbs combine the size and quick starting of incandescent bulbs

      with the power savings of fluorescent. While costing more to purchase than either incandescent or regular fluorescent, the cost is offset by the much longer life when compared to incandescent and the ability to work in ordinary fixtures when compared to regular fluorescent.

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