Quick Start Guide to LED Lighting Terms

Check out this LED glossary to give you a jump-start on your next LED project.

LED lighting is quickly approaching a tipping point from being an alternative solution to supplanting traditional lamps as the standard in lighting. The increasing adoption of LED (Light Emitting Diode) lighting in homes and businesses is due to its lower energy costs, longer life, increased sustainability and the fact that costs have come down drastically in recent years.

With new LED technology and products hitting the market every day, staying up-to-date on the latest terms and definitions isn't easy. Check out this LED glossary to give you a jump-start on your next LED project.

Binning: LED manufacturers sort their products into bins, based on lumen output and color. Fixture manufacturers specify a range of bins, from which they will accept LEDs. If they only accept LEDs from bins that are very close together, the diodes are more expensive, but result in a higher quality fixture. If fixtures are built with LEDs from a wider range of bins, cost and lead-time are reduced, but the variability of fixture performance is substantially decreased. Manufacturers may refer to their “tightly binned” products when they want to convey that theirs is a higher quality product.

Color Rendering Index (CRI): Measure of the degree of color shift that objects undergo when illuminated by the light source, as compared with the color of those same objects when illuminated by a reference source of comparable color temperature.

Color Temperature: Light is measured in Kelvins ranging from 9000K (which appears to be blue) down to 1500K (which appears orange-red). Color temperatures of 4000K or higher are considered cool, 3100K or less are considered warm. 5500K is closer to sunlight at noon.

An advanced controls system can monitor the available sunlight and offset the electric lighting needed to properly light a space

Daylight Harvesting: To reduce energy consumption, an advanced controls system can monitor the available sunlight and offset the electric lighting needed to properly light a space.

Driver: All LED fixtures include an LED driver or power supply. Just to make it confusing, though, this driver can be integrated into the fixture, separate from the fixture or remotely located. Typically, the driver is an important part of every LED system, and you should remember it is a factor when using LED fixtures.

Dynamic White: Some white LED fixtures can offer a range of white color temperatures, from a warm 2700K to a cool 6000K. There are different names for this technology, including variable white, adjustable white, tunable white and dynamic white. Again, a controller is required to adjust the light from a warm white hue to a cool white hue.

Foot Candles or Lux: The unit of measurement indicating how much illumination is reaching a surface.

IES (Illuminating Engineering Society): an organization dedicated to “improve[ing] the lighted environment by bringing together those with lighting knowledge and by translating that knowledge into actions that benefit the public.” The IES has developed, distributed and promoted the adoption of standards related to LED technology.

L70: L70 describes the brightness of an LED after a number of hours – often 50,000. If a product claims L70 after 50,000 hours, it means that after 50,000 hours of burning (nearly six years if the lights are on 24/7) the lights are now 70% as bright as they were when they were first installed. L70 doesn’t mean anything without the corresponding number of hours. You may also see terms such as L70 at 6,000 hours. Sometimes manufacturers will list L80 (or even L90) at 50,000 hours. This simply means that after 50,000 hours, the LEDs will be 80% (or 90%) as bright as they were initially. Be careful not to confuse L70 with LM79 or LM80!

Lamp Lumen Depreciation (LLC): Multiplier factor in illumination calculations for reduction in the light output of a lamp over a period of time.

Lighting Power Density: Watts per square foot. This can vary by how a space is used and its occupancy.

Lighting Power Density: Watts per square foot. This can vary by how a space is used and its occupancy

LM79: This IES document applies to LED fixtures (but not to components). It prescribes the approved method for “Electrical and Photometric Measurements of Solid-State Lighting Products.” In the beginning, LED products were the “Wild, Wild West”. Manufacturers claimed just about anything, based on their own personal “test procedures.” LM79 gave structure to the chaos and today LM79 compliance can help ensure that you are “comparing apples to apples” when you read LED product literature.

LM80: This IES document describes the approved method for “Measuring Lumen Maintenance of LED Light Sources.” It applies to bare LED light sources and does not cover complete luminaires (fixtures.) The main story here is usable life. LED sources, like the old metal halide lamps, tend to fade over life instead of “burning out.” Again, when manufacturers are using the same test methodology, you can be comfortable when comparing products.

Lumens: The total quantity of light produced by a lamp/fixture. These are units of measurement that describe the brightness that comes from a source of light. While lumens do not describe the quality of that light, it is used to show how much light is being generated. Generally speaking, the more lumens present, the brighter the light. For example, a traditional 60 watt incandescent bulb produces 800 lumens, which will generally light up an average-size room. An LED bulb will produce roughly the same number of lumens for a mere 12 watts of electricity.

Lumens per watt (LPW): This is a rating used for light bulbs which determines how much light is produced for each watt of electricity that is used. A good comparison is how many miles per gallon a vehicle gets on the road. For example, incandescent bulbs produce roughly 20 lumens per watt, while many of the newer LED bulbs produce anywhere from 80 to 100 lumens per watt. The greater the LPW, the less energy needed to light up a particular area.

Luminance: The intensity of the light.

RGB: RGB stands for Red, Green and Blue. An RGB LED fixture has all three colors of LEDs, which when blended can create almost any color, including white. This is the technology used in most of today’s fabulous color-changing light fixtures. Sometimes manufacturers use four different LED colors in their fixtures – RGBW. RGBW fixtures include a separate high quality white LED. A special controller is required to change the color of the fixture in an RGB or RGBW product.

Color temperatures of 4000K or higher are considered cool, 3100K or less are considered warm. 5500K is closer to sunlight at noon

SSL: LED fixture systems use semiconductor technology instead of filaments or arc tubes. SSL is the abbreviation for Solid State Lighting and refers to any type of lighting that uses diodes for illumination.

Warm Dim: With an incandescent lamp, the more you dim it, the warmer in color it becomes. When you dim it all the way down it becomes just a glowing orange filament. However, when an LED is dimmed, the color temperature does not change. Some people prefer this warm color temperature at low light levels, or just want their LED fixtures to better mimic incandescent. Warm dim technology is achieved by incorporating red and/or amber LED diodes into a white LED light fixture. Control technology is used to illuminate the warm sources as the fixture is dimmed to low levels.

Watt: This is a unit for measuring electrical power. This is the standard unit of power which is represented by being one joule of energy per second. A watt demonstrates the rate of electrical consumption over a period of time while the electrical device is in operation. Essentially, the electrical cost of operating an electrical device is calculated in terms of watts for the time it is being used.

Tunable lighting: Lighting that can change color temperature to adapt to specific applications. Tunable lighting has the potential to boost worker or student concentration, optimize retail lighting for specific merchandise or time of day, or increase patient mood in medical facilities.