In sodium-vapor lamps, illumination is created by using an electric current to excite sodium molecules. Excited sodium molecules emit light along a very narrow wavelength that corresponds to the color yellow, giving sodium-vapor lamps a characteristic amber glow. Since the light falls on such a narrow wavelength, colors are often difficult to distinguish under sodium-vapor illumination. Sodium-vapor lamps come in low pressure and high pressure formats.

High Pressure Sodium systems were developed to counteract some of the drawbacks of using a sodium-vapor lamp. The sodium is placed under pressure and additional elements are added in order to reduce lamp size and expand the emitted color wavelength. However, the light emitted still retains the characteristic yellow color and color rendering suffers. Sodium-vapor systems are still in use today due to their efficiency and decent lamp life of 20,000 hours.

High Pressure Sodium systems were developed to counteract some of the drawbacks of using a sodium-vapor lamp. The sodium is placed under pressure and additional elements are added in order to reduce lamp size and expand the emitted color wavelength. However, the light emitted still retains the characteristic yellow color and color rendering suffers. Sodium-vapor systems are still in use today due to their efficiency and decent lamp life of 20,000 hours.

Disadvantages:

  • Monochromatic light – Since the light emitted is largely in the yellow wavelength, colors will be distorted and difficult to distinguish.
  • Color Temperature – 2100K, gives an orange/yellow tinge to all illuminated objects.
  • CRI – 21, impossible to distinguish between a large range of colors.
  • Security concerns – Images captured by security cameras in areas lit by sodium-vapor will come out blurry, especially if subject is in motion. Makes identification difficult.
  • Unattractive – Blankets entire area with an unnatural, yellow tinge.