lighting terminology

  1. Splendor

    Knowledge What is lumen maintenance?

    Lumen maintenance or luminous flux maintenance refers to the remaining luminous flux over the initial flux (typically expressed as a percentage) at any selected elapsed operating time. LED packages rarely fail catastrophically (i.e., instantaneously stop emitting light), but rather experience...
  2. Splendor

    Knowledge What is a luminaire?

    A luminaire, more commonly known as a light fixture, refers to a complete lighting unit that controls and distributes light emitted from one or more light sources. Conventional light fixtures are lamp-based luminaires of which the light sources can be incandescent, fluorescent, high-intensity...
  3. Splendor

    Knowledge What is a lamp?

    “Lamp” is a generic term for a man-made light source created for receiving electrical power and for generating optical radiation. Lamps are designed and constructed according to universal standards established for bases, sizes and shapes, allowing for the substitution of lamps by other...
  4. Splendor

    Knowledge What is luminaire efficacy?

    Luminaire efficacy is the total luminous flux emitted by a luminaire divided by the total power consumed by the luminaire, expressed in lumens per watt (lm/W). Luminaire efficacy is a product of the wall plug efficiency (WPE) times the conversion efficiency (CE).
  5. Splendor

    Knowledge What is wall plug efficiency?

    Wall plug efficiency (WPE) is the efficiency of energy conversion from electrical power (W) to optical power (radiant flux in watts).
  6. Splendor

    Knowledge What is luminous efficacy?

    Luminous efficacy is the ratio of luminous flux to applied power and is expressed in output lumens per watt (lm/W). Unless otherwise noted, luminous efficacy indicates the ability of a light source or lighting system to convert electrical power to light perceptible by the human eye. Luminous...
  7. Splendor

    Knowledge What is illuminance?

    Illuminance is the area density of luminous flux incident at a point on a surface. In the International System of Units (SI), illuminance is measured in lux (lx). In the United States Customary System, the unit is footcandle (fc). One lux is one lumen per square meter. One footcandle is one...
  8. Splendor

    Knowledge What is luminance?

    Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. To put it simply, luminance is the amount of light coming from a surface. Luminance is often associated with brightness which relates to the strength of sensation resulting from...
  9. Splendor

    Knowledge What is luminous intensity?

    Luminous intensity (sometimes called candlepower) is a measure of luminous flux (wavelength-weighted power) emitted by a light source in a particular direction per unit solid angle. It can be described as the concentration of light in a particular direction. Luminous intensity is given in lumen...
  10. Splendor

    Knowledge What is candela?

    Candela (symbol: cd) is the base unit of luminous intensity which is a measure of the wavelength-weighted power emitted by a light source in a given direction per unit solid angle. One candela is one lumen per steradian (lm/sr).
  11. Splendor

    Knowledge What is luminous flux?

    Luminous flux is a measure of the flow of visible radiant energy emitted in all directions by a light source. It is a weighted sum of the radiant power at all wavelengths in the visible band. Electromagnetic radiation outside the visible band does not contribute to luminous flux. Unless...
  12. Splendor

    Knowledge What is footcandle?

    Lux (symbol: fc) is the SI unit of illuminance, a measure of how much luminous flux is spread over a given area. One footcandle is one lumen per square foot (lm/ft2).
  13. Splendor

    Knowledge What is lumen?

    Lumen (symbol: lm) is the SI unit of luminous flux (radiant power) which is the time rate of flow of radiant energy. Lighting products are commonly labelled with their light output in lumens.
  14. Splendor

    Knowledge What is the electromagnetic spectrum?

    The electromagnetic spectrum is a continuous range of electric and magnetic radiation that spans all wavelengths—from gamma rays which have a wavelength of 10 nanometers to radio waves which have a wavelength of 1012 nanometers. Within the spectrum electromagnetic radiation between 380 and 770...
  15. Splendor

    Knowledge What is a wavelength?

    Wavelength is the distance of one full cycle of the oscillation made by a photon. The distance is determined by the amount of energy which a photon carries. Photons containing more energy have shorter wavelengths, and longer wavelength photons carry low energy. The electromagnetic spectrum spans...
  16. Splendor

    Knowledge What is a photon?

    A photon is a particle or packet of light that represents a quantum of radiation energy. The amount of energy which a photon carries determines the amount that the photon vibrates and its wavelength.
  17. Splendor

    Knowledge What is task lighting?

    Task lighting is employed to illuminate an area where a specific task takes place. Task lighting ensures ample, focused light to support visual performance. It's a fundamental component of a layered lighting design in which lighting is composed of ambient, task and accent layers. Task lighting...
  18. Splendor

    Knowledge What is ambient lighting?

    Ambient lighting is the primary layer of light in an interior space. It's designed to fill a space with a soft level of overall light that makes navigating the space visually comfortable while providing other basic visual recognition. Although ambient lighting is often referred to as general...
  19. Splendor

    Knowledge What is general lighting?

    General lighting is designed to provide a substantial uniform level of illuminance throughout an area. This level of illumination all parts of a room can be safely navigated and establishes the overall impression an occupant has of the space. In a layered lighting scheme, general lighting is...
  20. Splendor

    Knowledge What is wall wash lighting?

    Wall washing is a form of accent lighting that involves illuminating a wall from top to bottom (or from bottom to top) in a smooth, graded wash of light. Wall wash lights create an even wide flood of light that bathes an entire wall in uniform light. A uniform distribution of illuminance across...
  21. Splendor

    Knowledge What is wall grazing?

    Grazing is a technique used to bring out the textured beauty of an interior or exterior vertical surface or architectural element. Grazing enhances a wall by placing the light fixture closer to the wall and aiming the beam upward or downward. How close the light fixture should be to the wall...
  22. Splendor

    Knowledge What is cove lighting?

    Cove lighting utilizes perimeter coves to conceal light sources. Light is bounced toward the ceiling or upper wall, projecting a pleasant lighting pattern on the ceiling and providing a soft, low level ambient light for the space. Light sources are shielded by a ledge or horizontal recess. Cove...
  23. Splendor

    Knowledge What is valance lighting?

    Valance lighting is provided by a length of light module shielded by a panel parallel to the wall at the top of a window. Light produced by the shielded light module bounces both upward and downward, which minimizes shadows and glare.
  24. Splendor

    Knowledge What is cornice lighting?

    Cornice lighting, also known as soffit lighting, directs light down from behind a soffit or cornice, washing the wall with light. The light source or light fixture is shielded by a panel parallel to the wall and attached to the ceiling. Modern cornice lighting is usually provided by LED strip...
  25. Splendor

    Knowledge What is accent lighting?

    Accent lighting directs concentrated beams of light to emphasize a particular object or surface feature, or to draw attention to a part of the field of view. Accent lighting is designed to provide focal illumination for highlighting objects such as paintings, photos, sculpture, or merchandise...