© International Dark-Sky Association Lighting 101; A few basics International Dark-Sky Association

© International Dark-Sky Association Lighting A complex topic ! But very important to everyone. We’ll look at only a few things here. Remember, it is vision that counts.

© International Dark-Sky Association Why night lighting? For work. For recreation. Fun. For safety and security. For amenity. For advertising or display. Marketing.

© International Dark-Sky Association Where to light, and when? Only where and when needed! Avoid obtrusive light. No wasted light or energy.

© International Dark-Sky Association Lighting Zones LZ 0 Very dark. LZ 1 Dark. LZ 2 Low ambient light. LZ 3 Medium ambient light. LZ 4 High ambient light.

© International Dark-Sky Association 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.

© International Dark-Sky Association Terms to know Light Intensity (candela) Flux (lumen) Illuminance (lux) Luminance (cd/sq meter) Power consumption (watt) Inverse square law

© International Dark-Sky Association 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.

© International Dark-Sky Association Electromagnetic Spectrum

© International Dark-Sky Association Cone and Rod Sensitivity Curves

© International Dark-Sky Association 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.

© International Dark-Sky Association A view of the eye

© International Dark-Sky Association Luminous intensity Unit: candela (cd) The “force” generating the flux. There’s a complicated definition.

© International Dark-Sky Association 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.

© International Dark-Sky Association 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.

© International Dark-Sky Association 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.”

© International Dark-Sky Association Schematic of the terms

© International Dark-Sky Association Some luminance examples Typical clear sky3000 cd/m 2 Typical overcast sky 300 Typical night sky in big city 3 Average dark sky site watt incandescent HPS lamp Desk top 70 Inside wall 40 Carpet 10

© International Dark-Sky Association 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.

© International Dark-Sky Association For example

© International Dark-Sky Association Some relations 1 fc = lux 1 meter = feet 1 fc = 1 lumen per sq foot

© International Dark-Sky Association Light levels Photopic. Cones. Color. Day vision. –The What System. Mesopic Scotopic. Rods. No color. Night vision. –The Where System.

© International Dark-Sky Association Cones and Rods

© International Dark-Sky Association The sensitivity curve

© International Dark-Sky Association Light Sources Flame. Incandescent. Mercury vapor. High pressure sodium. Metal halide. Low pressure.

© International Dark-Sky Association Quality lighting Maximizes the desired effects. –Good vision. –Good night ambiance. Minimizes the adverse effects. –Glare –Light trespass –Energy waste –Sky glow

© International Dark-Sky Association 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.

© International Dark-Sky Association Shielding Minimize glare. Minimize direct up light. Minimize light trespass. Control the light output.

© International Dark-Sky Association Unshielded Fixture

© International Dark-Sky Association Shielded Fixture

© International Dark-Sky Association 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

© International Dark-Sky Association Contrast and Visibility

© International Dark-Sky Association Colo Contrastr Color Contrast Color Contrast Color Contrast Color Contrast Color Contrast

© International Dark-Sky Association Color Contrast Color Contrast Color Contrast

© International Dark-Sky Association A few visual examples What is the bad lighting? Why? What is the good lighting? Why?

© International Dark-Sky Association A glary street light doing a good job of lighting a tree but not much else.

© International Dark-Sky Association Almost a definition of light trespass, at an installation in San Francisco.

© International Dark-Sky Association Glare, luminance overload,Better design! bad transition lighting.

© International Dark-Sky Association A major street in San Francisco.

© International Dark-Sky Association Typical car lot?Much better!

© International Dark-Sky Association A billboard, seen from the side.

© International Dark-Sky Association A typical full cut-off lighting fixture, as used for street lighting.

© International Dark-Sky Association A good use of full cut-off fixtures.

© International Dark-Sky Association Here is an example of How To Do It, if one wants both the nice appearance in the day and good lighting at night.

© International Dark-Sky Association Here’s a good residential fixture.

© International Dark-Sky Association Here is another good example, using lighting fixtures with good control of the light output.

© International Dark-Sky Association Signs can be well done too.

© International Dark-Sky Association Lighting Ordinance? The process educates many people. It promotes good lighting. It sets a community standard. When needed, it is the law.

© International Dark-Sky Association 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.

© International Dark-Sky Association

International Dark-Sky Association 3225 N. First Ave. Tucson, AZ Phone: Fax: