comfort, 照明, lighting, science, visual

If Light Is Not What You Expect

radiation-law
DUBAI, UAE. A question from a client has recently prompted to digg into a question why dimming LED does not feel like dimming conventional halogen spotlights. They have refurbished a restaurant and replaced spotlights with halogen lamps to LEDs. The effect did not impress: instead of warm ambience the client got pale dull environment.
The phenomenon of warmth in a dimmed halogen lamp is achieved through cooling down the tungsten filament. Less current passing through it gives out a redder spectrum of the light. Naturally we are expecting warmer hues from lesser light!
LED light source uses a different physical mechanism: electroluminescence. Halogen lamp is still incandescent in its nature. There is no major change in the color of the light when the current passes through an LED die. This change, in fact, is not discernible to the human eye. The color of light in an LED depends on the chemicals used to coat the LED die, and not on the thermal radiation.
Hope we have not yet lost you by the fourth passage. Because here is the good news:  the industry has a solution to offer. LED Engin from the USA has developed a light source which combines several dies driven separately which helps to imitate a shift from 3000K to 1800K (your incandescent lamp is 2700K, and your candle is 1700K).
Adopted from LEDs Magazine
Originally posted on Lightintelligence.bogspot.com in Nov 2013
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