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Luminaire Light Distribution Classifications


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A summary of the schemes used in the lighting industry to classify luminaire light distributions

Published in: Engineering
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Luminaire Light Distribution Classifications

  1. 1. Luminaire light distribution basics Presented by Morgan Catha, Grandlite Product Development Engineer September 26, 2014
  2. 2. Photometry concepts Lumen: A quantity of emitted light energy in the visible spectrum (“luminous flux”). Defined in terms of the sensitivity of the human eye to light. One lumen is 1/683 watts or more of visible light energy, depending on the spectrum of the light source.
  3. 3. Candela: A measure of “luminous intensity”, defined as lumens per solid angle (measured in steradians). Expresses how much light is being emitted in a particular direction. Photometry concepts
  4. 4. Footcandle: A measure of “illuminance”, the amount of visible light energy falling on a surface. Defined as one lumen per square foot. Another common unit is “lux”, equal to one lumen per square meter. Photometry concepts
  5. 5. Luminance: An expression of the intensity of light leaving a surface in a particular direction. Measured in candelas per square meter. Photometry concepts
  6. 6. “Brightness”
  7. 7. “Brightness” ‘"Brightness" should be used only for nonquantitative references to physiological sensations and perceptions of light.’ -- Federal Standard 1037C, the Federal Glossary of Telecommunication Terms (1996)
  8. 8. Photometric Testing Rotating mirror Goniophotometer -- measures light output
  9. 9. Grandlite goniophotometry laboratory Photometric Testing
  10. 10. A type C rotating mirror goniophotometer is used to record candela values for each angle Photometric Testing
  11. 11. The candela values are stored in a .ies file Photometric Testing
  12. 12. Photometric Reports Polar candela plot • Shows cross-sections of light intensity • Useful for seeing the overall shape of a luminaire’s light distribution
  13. 13. Photometric Reports Isoilluminance plot • Shows lines of equal illuminance on target surface • Useful for seeing how a luminaire illuminates the area around it
  14. 14. Photometric Reports Luminaire Classification System Graph • Shows backlight, uplight and glare by sector • Useful for seeing how the BUG rating is determined
  15. 15. B.U.G. Rating
  16. 16. B.U.G. Rating
  17. 17. B.U.G. Rating
  18. 18. B.U.G. Rating
  19. 19. B.U.G. Rating
  20. 20. IES Cutoff Classifications
  21. 21. IES Cutoff Classifications
  22. 22. IES Cutoff Classifications
  23. 23. IES Cutoff Classifications
  24. 24. IES Roadway Types
  25. 25. IES Roadway Types • Type I - Half-maximum candela trace falls between 1 MH LRL on the House side and 1 MH LRL on the Street side • Type II - Half-maximum candela trace on the Street side is beyond the 1 MH LRL but not beyond the 1.75 MH LRL • Type III - Half-maximum candela trace on the Street side is beyond the 1.75 MH LRL but not beyond the 2.75 MH LRL • Type IV - Half-maximum candela trace on the Street side is beyond the 2.75 MH LRL • Type V - Has circular symmetry being essentially the same at all lateral angles around the luminaire • Type VS - Zonal lumens (below 90-degress vertical) for each of the eight horizontal octants (0-45, 45-90, 90-135, 135,180, 180-225, 225- 270, 270-315, 315-360) are within +-10% of the average zonal lumens of all octants
  26. 26. IES Roadway Types • Very Short (VS): The maximum intensity points to a point in the VS zone of the grid, 0-1.0 MH TRL • Short (S): The maximum intensity points to a point in the S zone of the grid, 1.0 - 2.25 MH TRL • Medium (M): The maximum intensity points to a point in the M zone of the grid, 2.25 - 3.75 MH TRL • Long (L): The maximum intensity points to a point in the L zone of the grid, 3.75 - 6.0 MH TRL • Very Long (VL): The maximum intensity points to a point in the VL zone of the grid, > 6.0 MH TRL
  27. 27. IES Roadway Types
  28. 28. IES Roadway Types • Maximum candela point furthest lateral point between 2.25 and 3.75 mounting heights = Medium • Half maximum candela trace furthest longitudinal point between 1.75 and 2.75 mounting heights = Type 3
  29. 29. IES Flood Types
  30. 30. IES Flood Types BeamField 10% of maximum candela 50% of maximum candela Maximum candela
  31. 31. IES Flood Types Example: NEMA 7x7 means the field angle is 130 degrees or wider in both the horizontal and vertical planes. For short, “NEMA 7”.