Lighting 101; A few basics International Dark-Sky Association darksky 520.293.3198

1. Lighting 101;A few basicsInternational Dark-Sky Associationwww.darksky.org520.293.3198

2. Lighting • A complex topic ! • But very important to everyone. • We’ll look at only a few things here. • Remember, it is vision that counts.

3. Why night lighting? • For work. • For recreation. Fun. • For safety and security. • For amenity. • For advertising or display. Marketing.

4. Where to light, and when? • Only where and when needed! • Avoid obtrusive light. • No wasted light or energy.

5. Lighting Zones • LZ 0 Very dark. • LZ 1 Dark. • LZ 2 Low ambient light. • LZ 3 Medium ambient light. • LZ 4 High ambient light.

6. How much light? • Use Illuminating Engineering Society (IES) or International Commission on Illumination (CIE) recommended levels. • “The More the Better” is a myth. • By Lighting Zone. • Consider the location where you are. • Use good transition lighting. • Remember the eye must adapt.

7. Terms to know • Light • Intensity (candela) • Flux (lumen) • Illuminance (lux) • Luminance (cd/sq meter) • Power consumption (watt) • Inverse square law

8. Light • Radiant energy capable of causing a visual sensation. • Individuals vary greatly in their sensitivity. • The eye sensitivity curve. Color. • About 8 percent have non-normal color vision.

9. Electromagnetic Spectrum

10. Cone and Rod Sensitivity Curves

11. The Eye • Actually, it is the eye and brain system. • We can see over a huge range in brightness, but not at one time. • Adaptation is a critical element • 10 to 1, at the extreme 50 to 1. • The scale goes up and down with lighting level, and the presence of glare.

12. A view of the eye

13. Luminous intensity • Unit: candela (cd) • The “force” generating the flux. • There’s a complicated definition.

14. Luminous flux • Unit: lumen • There is a complicated definition. • An isotropic source of 1 cd gives 4 pi lumens on the spherical surface about it. (Area of the sphere is 4 pi sq units) • It is independent of the unit of radius.

15. Illuminance • Unit: lux (1 lumen per square meter) or footcandle (1 lumen per square foot) • Luminous flux per unit area of incident surface. It is what is received at the surface. • One can have horizontal, vertical, cylindrical illuminance.

16. Luminance • Unit: candela per square meter • What we see, the visual effect of the illuminance. Depends on the illuminance level, the properties of the surface, and the projected area on the plane perpendicular to view. • The “perceived brightness.”

17. Schematic of the terms

18. Some luminance examples • Typical clear sky 3000 cd/m2 • Typical overcast sky 300 • Typical night sky in big city 3 • Average dark sky site 6 10-4 • 60 watt incandescent 120000 • HPS lamp 1500000 • Desk top 70 • Inside wall 40 • Carpet 10

19. Inverse square law • The illuminance at a point varies with the luminous intensity (cd) and inversely with the square of the distance to the source. • The light emitted is spread out over a larger area as it gets further from the source.

20. For example

21. Some relations • 1 fc = 10.76 lux • 1 meter = 3.282 feet • 1 fc = 1 lumen per sq foot

22. Light levels • Photopic. Cones. Color. Day vision. • The What System. • Mesopic • Scotopic. Rods. No color. Night vision. • The Where System.

23. Cones and Rods

24. The sensitivity curve

25. Light Sources • Flame. • Incandescent. • Mercury vapor. • High pressure sodium. • Metal halide. • Low pressure.

26. Quality lighting • Maximizes the desired effects. • Good vision. • Good night ambiance. • Minimizes the adverse effects. • Glare • Light trespass • Energy waste • Sky glow

27. Keys to Quality Lighting - See the effect, not the source. - Shine the light down. - No glare. - Light only where and when needed. - Don’t over light. - Use energy efficient sources.

28. Shielding • Minimize glare. • Minimize direct up light. • Minimize light trespass. • Control the light output.

29. Unshielded Fixture

30. Shielded Fixture

31. Some Other Issues • Safety and Security. • The aging and disabled eye. • Human health. • Animals and plants. Our eco-system. • Energy. • Visibility. How we see: Contrast

32. Contrast and Visibility

33. Colo Contrastr Color ContrastColor ContrastColor ContrastColor ContrastColor Contrast

34. Color ContrastColor ContrastColor ContrastColor ContrastColor ContrastColor Contrast

35. A few visual examples • What is the bad lighting? • Why? • What is the good lighting? • Why?

36. A glary street light doing a good job of lighting a tree but not much else.

37. Almost a definition of light trespass, at an installation in San Francisco.

38. Glare, luminance overload, Better design! bad transition lighting.

39. A major street in San Francisco.

40. Typical car lot? Much better!

41. A billboard, seen from the side.

42. A typical full cut-off lighting fixture, as used for street lighting.

43. A good use of full cut-off fixtures.

44. Here is an example of How To Do It, if one wants both the nice appearance in the day and good lighting at night.

45. Here’s a good residential fixture.

46. Here is another good example, using lighting fixtures with good control of the light output.

47. Signs can be well done too.

48. Lighting Ordinance? • The process educates many people. • It promotes good lighting. • It sets a community standard. • When needed, it is the law.

49. Purpose of a Lighting Code: • Limit obtrusive lighting. • Promote good business. • Promote the community. • Help everyone see better. • Save energy. • Preserve dark skies for all.