Posted by Phil Rhodes on April 30, 2013 •
Image by Pete Smith, courtesy of Hexolux •
“I should probably start with an apology: this one is going to get technical. Still, I hope you’ll stick with it, because understanding how and why we take such care over measuring the quality of white light is key to understanding the benefits of modern lighting equipment such as that based on fluorescent and LED sources. Even more crucially, it’s also key to understanding the potential problems, and the sort of tactics available to the average snake-oil salesman to cover up those problems.
Most of us know that white light is made up of a mixture of all the colors in the spectrum, or to be a bit more scientific about it, all the visible wavelengths of radiation. Wavelengths of light are short – 550 nanometers is green, 700 red and about 450 a really deep blue. The problem, which is fairly well known, is that almost no lighting equipment emits the same amount of light at every wavelength. Scientifically, they have a non-uniform spectral power distribution. If you are trying to illuminate an object that reflects light at a rather specific wavelength that is absent from the so-called white light you’re shining on it, you may have a problem that’s impossible to predict just by looking at things with your eyes.”
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