Page 3 - Microsoft Word - Competitve Analysis, Color Rendering, MH, Fluorescent, SSL.docx

Spectral Distribution

Spectral distribution charts the intensity of each wavelength relative to the highest intensity wavelength
of the given light source. Some white lights have more red, others may emit more blue. Some have
wide gaps in their distribution while others cover the visible wavelengths more consistently.

METAL HALIDE FLUORESCENT SOLID STATE

Figure 2. IES 2012 Design Guide for Choosing Light Sources for General Lighting (2)

Figure 2 is an excerpt published by the Illuminating Engineering Society (IES), the unbiased governing
body for standards in the lighting industry. This shows the spectral distributions of metal halide,
fluorescent, and solid state, respectively.

In reading spectral distributions, the intensity in each wavelength is relative to the maximum intensity of
the highest single wavelength. A perfect spectral distribution would be flat, balancing the intensities
across all wavelengths.

As you can see, metal halide and fluorescent have a very “spiked” distribution; they are distributed in
very narrow spectral bands and very weak in between. Conversely, the nature of the SSL delivers a
more broad spectral distribution.

Figure 3 shows an overlay of the IES
spectral distribution charts from above,
comparing fluorescent and SSL. The red
illustrates the additional spectral bands
provided by the SSL while the blue shows
the additional provided by the fluorescent
technology.

Because the wavelengths are more evenly
distributed, the SSL has significantly better
color rendition.

If this is the case, how is it that these two
sources can exhibit similar CRIs?
Figure 3. Spectral Band Comparison; Fluorescent to SSL

Competitive Analysis, Color Rendering in White Light Page 3