Of an electromagnetic source, especially in the optical regime, the hue or wavelength (spectral content) expressed or specified as the hypothetical wavelength (s) emitted by an ideal blackbody having an absolute temperature of n kelvins (n K. ) Note 1: Higher numbers indicate hues in or toward the blue; lower numbers indicate hues in or toward the red. Note 2: Examples of color temperature are approximately 5000 K to 5500 K (daylight,) approximately 4100 K (fluorescent lighting,) and approximately 2800 K (incandescent. ) Note 3: Color temperature is commonly used to characterize ambient lighting or lighting employed for photographic purposes.