LEDs, or Light Emitting Diodes, are small semiconductors that emit light when an electric current is applied. They have existed since the early 1960’s as low power LEDs and have mainly been used in electronics until recently. When high power LEDs were invented, they revolutionize the lighting market and boasted numerous advantages over existing technologies. They produce light with very little heat and without the use of gases or incandescent filaments.
Frequently Asked Questions
What are LEDs?
Why are LEDs better than traditional lighting?
There are many reasons that LEDs are better, but the most drastic differences are the 60% to 80% reduction in energy consumption and the over 5 times longer life.
Is LED technology more expensive?
LED fixtures demand a higher upfront cost than their HID counterparts, but the energy and maintenance savings associated with LEDs will more than pay for the difference in a very short period of time. When you consider value, it can be argued that LED fixtures are not more expensive at all. LED fixtures must be made of metal that can radiate heat; also they use micro processors instead of ballasts. So, for a slightly higher cost you are getting a more durable fixture with greater technological capabilities.
Can LEDs be screwed into HID fixtures?
No. Because of the difference in the way LEDs and HIDs operate and dissipate heat, a whole fixture change-out is necessary.
Can the color of an LED be changed?
Yes and no. LEDs can produce different colors, but they have to be constructed with that color in mind. Once the LED is manufactured the color output is fixed. A fixture containing an array of colored LEDs can produce different color outputs by mixing varying spectrums and intensities of color.
Why do some manufacturers claim that their LED lasts 100,000 hours?
On average, after 50,000 to 60,000 hours 90% of the LEDs in a fixture will operate at 100% and 10% will degrade by 10%. So, the LEDs may last well beyond 60,000 hours, but they will most likely experience lumen degradation.
Terminology & Definitions
LUX - The lux (symbol: lx) is the SI unit of illuminance and luminous emittance measuring luminous power per area. It is used in photometry as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface.
Foot Candle - A foot-candle (sometimes foot candle; abbreviated fc, lm/ft², or sometimes ft-c) is a non-SI unit of illuminance or light intensity widely used in photography, film, television, conservation lighting, and the lighting industry.
The unit is defined as the amount of illumination the inside surface of a 1-foot radius sphere would be receiving if there were a uniform point source of one candela in the exact center of the sphere. Alternatively, it can be defined as the illuminance on a 1-square foot surface of which there is a uniformly distributed flux of one lumen. This can be thought of as the amount of light that actually falls on a given surface. The foot-candle is equal to one lumen per square foot.
Lumens - The lumen (symbol: lm) is the SI derived unit of luminous flux, a measure of the power of light perceived by the human eye.
Efficacy - In lighting design, "efficacy" refers to the amount of light (luminous flux) produced by a lamp (a light bulb or other light source), usually measured in lumens, as a ratio of the amount of power consumed to produce it, usually measured in watts. This is not to be confused with efficiency which is always a dimensionless ratio of output divided by input which for lighting relates to the watts of visible power as a fraction of the power consumed in watts.
Photometry - Photometry is the science of the measurement of light, in terms of its perceived brightness to the human eye.
IES - IES stands for Illuminating Engineering Society. IES standard file format was created for the electronic transfer of photometric data over the web. It has been widely used by many lighting manufacturers and is one of the industry standards in photometric data distribution. An IES file is basically the measurement of distribution of light (intensity) stored in ASCII format. You can think of it as a digital profile of a real world light. In 3d software like 3ds max it can be used for creating lights with shapes and physically accurate form.
LM-79 - LM-79 is an IES testing procedure for the Electrical and Photometric Measurements of Solid State Lighting
LM-80 - LM-80 is an IES testing procedure for Measuring Lumen Maintenance of LED Light Sources. LM-80 covers the measurement of lumen maintenance of LED packages, arrays and modules
