What is spectral power distribution?
The visible part of the electromagnetic spectrum is composed of radiation with wavelengths from approximately 400 to 750 nanometers. The blue part of the visible spectrum is the shorter wavelength and the red part is the longer wavelength with all color gradations in between. Spectral power distribution graphs show the relative power of wavelengths across the visible spectrum for a given light source. These graphs also reveal the ability of a light source to render all, or, selected colors. Below see how a typical spectral power distribution graph for daylight. Notice the strong presence (high relative power) of ALL wavelengths (or the “full color spectrum”). Daylight provides the highest level of color rendering across the spectrum. Compare the daylight spectral power distribution with that for a particular fluorescent lamp. The most obvious difference is the generally lower level of relative power compared to daylight – – except for a few spikes. All wavelengths (the “full spectrum)