Lighting System Basics
Lighting can include overhead lighting, ambient lighting, task lighting, accent lighting, display lighting, or daylighting. Let's start with some of the terminologies in a lighting system. The most important term is a lamp, which is a light source, such as a light bulb or a fluorescent tube.
A luminaire is a complete lighting unit, which includes the lamp, reflector, ballast, socket, wiring, diffuser, and housing.
- Lamp refers to the manufactured light source or a man-made source of light.
- The ballast provides the circuit conditions such as voltage, current, and wavelength to operate a lamp.
- The reflector redirects the light through reflection.
- The diffuser redirects and/or scatters light through diffuse transmission.
For more definitions see the Lamp Lighting Glossary on the Technical Consumer Products, Inc. website. You can also check out the Lighting Made Easy infographic from Energy Star.
Common types of lamps include incandescent lamps, compact fluorescent lamps, and LED lamps. Comparing all three types of lamps, if they produce the same amount of light (measured in lumens) the LED lamps are the most efficient because they use a smaller amount of energy (measured in watts). To see a Lightbulb Efficiency Comparison Chart visit the Greater Cincinnati Energy Alliance website.
Lamps have different color temperatures, ranging from warm to cool. The light color is referred to as Correlated Color Temperature (CCT), and is measured in Kelvins (K). 2700K - 3000K is the range of warm light, 3000K-4000K is the range of neutral light, and 4000K-6500K is the range of cool light.
Below are different components of lighting measurements, and they represent some of the items you'll look for when out in the field.
- Light Output - Luminance is light reflected in a particular direction, and the luminous flux is the time rate of the flow of light. Luminous flux is measured in lumens. A lumen is the amount of light lamp emits once it’s started.
- Power - The rate at which energy is taken from an electrical system or dissipated by a load. The unit of power is a watt, a unit of electrical power equal to 1 joule per second.
- Efficacy - The efficiency of a light source, or the measurement of a lamp's performance, is measured by a ratio of the power that goes in and the service that comes out. It's expressed in lumens per watt (LPW or lm/W) and is calculated by dividing the light coming out of the source by the power going in.
- Lighting Power Density - The intensity of a light source, or a measurement of the intensity of the lighting power over a specific area, or square footage is expressed in watts per square foot (W/sf) and is calculated by dividing the watts of the light by the area it serves.
Resources from the UC Davis California Lighting and Technology Center
Visit their website to read case studies, guides, watch videos, and much more.
Read the Lighting Technology Overview to learn about LED Lamps, factors to consider when comparing LED products, and lighting controls.
Read the Non-Residential Lighting Guide to learn about lighting concepts, technology, and compliance requirement
Resources from the UC Davis Energy & Efficiency Institute
Other Resources
California Energy Commission LED Lamp Specification 3.0
Footcandle Recommendations from Guth
ASHRAE Standards for Lighting Power Densities
Helpful Blogs
From Engineered Products Co is the blog, Ask the Engineer, we particularly like this article.
The Lighting Controls Association covers several lighting topics, we like this infographic.
A book called Photonics- 50 Enlightening Infographics has a lighting chapter and is online here.