Home / Commercial Lighting / Why Kichler - For Pros / Technology Terms & Descriptions Technology Terms & Descriptions What Are LEDs? LEDs, or light emitting diodes, are semiconductor devices that produce visible light when an electrical current is passed through them. LEDs are a type of Solid StateLighting (SSL), as are organic light emitting diodes (OLEDs) and light emitting polymers (LEPs). How is LED lighting different than other light sources, such as incandescent and CFL? LED lighting differs from incandescent and compact fluorescent lighting in several ways. When properly designed, LED lighting solutions can offer higher efficiency, increased durability, and significantly longer life than traditional light sources. Traditional lighting products leverage standard bulb shapes and historical base types (Example: A19 with E26 medium base). LED lighting products, on the other hand, incorporate custom light sources and application-specific electronics. Compared to the traditional lighting technologies of Incandescent (light is produced by heating a tungsten wire) and Compact Fluorescent (light is produced by exciting phosphors with the emission of mercury), LEDs produce visible light by passing current through a solid state diode. The solid state diode converts electrical energy into photons, and the color of the photon is defined by the selection of materials used to fabricate the diode. For example, red LEDs are typically produced with an AlInGaP diode (Aluminum/ Gallium/Indium/Phosphide), and green LEDs are produced with an InGaN diode (Indium/Gallium/ Nitride). There are several LED design approaches for producing white light. The most sophisticated of these is mixing red, green and blue LEDs to achieve a given white colorpoint. This approach can achieve high efficiency, however, usually requires complex electrical circuitry and can lead to higher costs. The most simplistic and commonapproach used today leverages a blue LED, fabricated with an InGaN diode, and a phosphor material that produces a yellow/orange spectrum. The combination of blue andyellow/orange spectrums provides a white color point. White LEDs have made significant increases in efficiency, or LPW (lumens per watt), over the past three to four yearsand have begun to penetrate most general lighting applications. LUMENS: Light Output vs. Energy Consumed For decades, consumers have purchased light bulbs based on consumed wattage, for example, a 60W Incandescent light bulb. However, as new lighting technologies offer more efficient solutions, consumers are now able to replace the older 60W Incandescent bulbs with either a 13W CFL or 11W LED product, while maintaining the same lightlevels in their application. For this reason, the focus of light sources has shifted from energy consumed (60W) to light levels produced (800 Lumens). Lumens (Lms) are ameasurement of the luminous flux, or light level, coming from a given light source. Typical light levels for traditional 40W, 60W, 75W and 100W Incandescent bulbs are 450Lms, 800 Lms, 1100 Lms and 1600 Lms respectively. COLOR METRICS: Color Temperature (Kelvin) and Color Rendering Index (CRI) A light’s appearance is traditionally defined by two color metrics; Color Temperature (in terms of degrees Kelvin), and Color Rendering Index (a number between 0 and 100). Color Temperature is best understood by referencing the Kelvin chart illustrated below. As seen on this chart, the warm glow of candlelight falls between 1,000 and 2,000 Kelvin. This lower portion of the scale also includes the traditional Incandescent light bulb, which typically produces a 2700K output at full power. As you move up the chartthe color appearance becomes cooler. 5000K is normally referenced when referring to Daylight, and 10,000K produces a very blue, cold light appearance. The Lighting Factslabel, shown to the right, also attempts to illustrate the color temperature range in order to help customers choose the best light source for their application. The Color Rendering Index, or CRI value of a light source attempts to quantify how accurate various colors appear under a given light source. CRI values typically range from 0 to 100, with 100 representing the highest correlation to a reference light source. Incandescence is most often the default light source when comparing Fluorescent and LED, and is used to generate a CRI value. Incandescence light sources offer the broadest spectrum and have become the default standard when comparing how a given light illuminates color. Simply put, how true do the greens, reds, browns, etc. appear under a given light source when compared to an Incandescent bulb?