Training Tip: Master these key terms and acronyms to improve customer communication

To help communicate effectively and provide clear solutions for your clients, it’s important to understand the numerous terms and acronyms in the lighting world. NXT Level’s Course 1: Lighting Concepts empowers you with mastery of not only the key terms, but their underlying concepts as well.


  • Spectral Power Distribution (SPD) is a pictorial representation of the radiant power emitted by a light source at each wavelength or band of wavelengths in the visible region of the electromagnetic spectrum (38 to 780 nanometers).

Light and Color

  • Color Correlated Temperature (CCT) is the absolute temperature of a blackbody whose chromaticity (color appearance) most nearly resembles that of the light source.
  • Color Rendering Index (CRI) is the measure of the degree of color that shift objects undergo when illuminated by the light source, as compared with the color of those objects when illuminated by a reference source.
  • Gamut Area Index (GAI) is a measure of color rendering based upon the range of colors achievable on a given color reproduction medium (or present in an image on the medium) under a given set of viewing conditions.

Photometry and Lighting Measurement

  • Luminous Intensity (Candela) is the luminous flux on a small surface centered on and normal to the direction divided by the solid angle (in steradians) that the surface subtends at the source. Luminous intensity can be measured in candelas or in lumens per steradian.
  • Luminous Flux (Lumen) is the luminous radiant power measured in lumens. This is the overall light output of a lamp or luminaire.
  • Illuminance (footcandles) is the amount of light (luminous flux) incident on the surface area. Illuminance is measured in footcandles (lumens/square foot).
  • Luminance is the photometric quantity most closely associated with the perception of brightness, measured in units of luminous intensity (candelas) per unit area (square feet).

For an online, on-demand refresher on these terms and their underlying concepts, you can always access NXT Level Course 1: Lighting Concepts, or any other training topic, once you’ve earned your designation.

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