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Question:

In the answer to another question you distinguished between full-spectrum and broad-spectrum ligths. What is the difference, and what kinds of lights produce each?

Answered by: Michael Terman

Neither term has exact technical meaning. Basically, they are short-hand to describe lamps that produce variations of white light.

Full-spectrum light contains a higher balance of short wavelengths, which creates a bluish, "cold" white, while broad-spectrum lamps create "softer" or "warmer" whites.

In technical terms, full-spectrum lamps have color temperatures of approximately 6000 Kelvin and higher, while broad-spectrum lamps range from about 3000-5000 Kelvin.

The dividing line is not distinct. Originally, "full spectrum" also implied a boost in ultraviolet radiation (great for plants, but not for human eyes and skin). Now one sees manufacturers confusingly describing their lamps as "UV-filtered full spectrum."

Bottom line: there are no established psychological or health benefits of full-spectrum light. The lamps are more expensive than other white fluorescent sources, and electrically less efficient.