Products/Options
When deciding which lights to choose, the most important factors are light output and color.
| Light Source | Typical Luminous Efficacy Range in lm/W (varies depending on wattage and lamp type) |
|---|---|
| Incandecent (no ballast) | 10-18 |
| Halogen (no ballast) | 5-20 |
| Compact fluorescent (CFL) (incl. ballast) | 35-60 |
| Linear fluorescent (incl. ballast) | 50-100 |
| Metal halide (incl. ballast) | 50-90 |
| Cool white LED >4000K (incl. driver) | 60-92* |
| Warm white LED <4000K (incl. driver) | 27-54* |
| *As of Spring 2009 | |
Light Output
Light output is measured either in lumens or in footcandles. As you can see from the table, LED’s can create the same amount if not more lumens per watt when compared to the other technologies.
However, The real gain in efficiency comes from the fact that LED’s deliver a directional light, which means they emit light in only one direction.
The conventional technologies emit light in all directions, which often means losing 40-50% of the light in the fixture. Footcandles, or lumens per square foot, are a measurement of how much light is hitting the surface. Since LED’s are directional, they typically are able to deliver more footcandles. (see graphic on right)
Correlated Color Temperature (CCT)
CCT describes the relative color appearance of a white light source, indicating whether it appears more yello/gold or more blue, in terms of the range of available shades of white. CCT is given in Kelvin (SI unit of absolute temperature) and refers to the appearance of a theoretical black body heated to high temperatures. As the black body gets hotter, in turns red, orange, yell, white, and finally blue. The CCT of a light source is the temperature (in K) at which the heated black body matches the color of the light source in question.
Color
The color of white light is measured by ColorTemperature. The lower the temperature, the more orange the light and the higher the temperature the more blue the light (See graphic to left).
Conversely, the Color Rendering Index measures how well the light renders colors. LED’s typically have a high color rendering index, which makes them ideal for applications such as retail stores, salons and car dealerships.