Light emitting diode, or LED, light sources are able to produce light from the electrons passing through the PN junction of the diode. There are many different types of LEDs that produce different wavelengths of light. White LEDs are a combination of different LEDs with unique spectra, combining to produce a white light color.

An LED bulb with more blue tones can have a higher correlated color temperature (CCT). Figure 5-3 shows the spectral plot of a 5000K LED bulb, and Figure 5-4 shows the spectral plot of a 2700K LED bulb. From these images, it can be observed that the spectrum of the 2700K bulb is shifted to the right, toward the longer wavelengths. Neither spectral plot has significant content in the NIR region, which is characteristic of all LED light sources.