LED Glossary – Common LED Terms – LED Resource Center


A unit of measurement of light output from a fixture. A standard 65 watt incandescent bulb emits about 800 lumens.
Alternating current, the type of current that comes off the power lines. This uses a line and neutral wire. Most of our line voltage fixtures are designed to run on 120VAC.
Direct current, the type of current used for most of our low voltage fixtures, such as 12VDC or 24VDC. This has positive and negative terminal connections and electricity only flows one way.
CRI / Color Rendering Index
This is one way of determining the quality of white light emitted by a fixture, and describes how well the light shows colors. It is a scale from 0 to 100.
CCT/Color Temperature
This is the most common method of measuring colors of white and differentiating between warm tones as low as 1000K, which is essentially red, or as “cold” as 10,000K, which is blue. Our most common color temperatures are between 3000K, 4000K, and 6000K.
An ampere is a common unit of measurement for electrical current draw.
Watts are used to determine power draw for light fixtures. Traditionally incandescent bulbs had their light output measured in watts, but with the advent of CFL, halogen, metal halide, and now LED technologies, the watt has become an unreliable method of measuring a fixture’s light output. That’s because a 65 watt incandescent may be roughly equivalent to a 15 watt fluorescent, and a 9 watt LED fixture.
This is the method used to categorize specific LED chips with similar characteristics. Because each chip is very slightly different, chip manufacturers use binning to more accurately represent color temperature, lumens, and voltage.
LED: Light Emitting Diode
A lighting technology that uses much less energy while have more flexibility and longer life span than other lighting technologies.
Solid state lighting
The technology used in LEDs. As opposed to incandescent bulbs which use thermal radiation, LEDs use electroluminescence to provide a better quality light.
Luminous Efficacy
Also known as luminous efficiency or lighting efficiency, this is simply a measure of how energy efficient a source of light is. It’s typically measured in lumens per watt. For example, a standard incandescent bulb can have around 8 lm/W, while many of aspectLED’s fixtures have nearly 100 lm/W. Even LED technology can vary in lumens per watt depending on size, quality, and color temperature of the individual LED chip(s). You can calculate any of aspectLED’s products’ luminous efficacy by dividing the lumens listed in the specifications by the fixture’s wattage.
Isocandela diagram
This is used to represent brightness or intensity of a light source in each direction.
A scientific instrument that measures the light output of lighting fixtures.
CRI: Color Rendering Index
A method of grading the color rendering ability of the light produced by a luminaire on a scale of 0-100. While technically possible for any color fixture, it is only a meaningful data point when referring to the various white color temperatures. With LEDs, this can often be a method of determining the quality of the LED chip, as poor quality chips will not emit the same quality of light.
IP: Ingress Protection
While this is typically referred to as waterproofing, it also measures whether dust and other objects can get inside an item. IP is usually followed by two numbers. The first number determines intrusion and dust protection on a scale of 1-7, and the second number measures moisture protection and water proofing on a scale of 1-9. Common ratings include IP65 (moisture and occasional water protection), IP67 (constant moisture, low pressure spraying, occasional immersion), and IP68 (completely sealed and submersible for use underwater at ordinary pressures).
Backlighting has many definitions, but our customers typically refer to it as a way to light something from behind to create a glowing light effect. Flexible LED Strip Lights are a popular choice for people looking to create a backlighting effect on mirrors, TVs, and virtually anything else.
By definition a diode is simply an electrical device that restricts electricity to flowing in one direction only – like a one way check valve for electrical current. However, in the LED industry it is slightly more specialized because an LED is actually a diode – a Light Emitting Diode. That leads many to refer to use the terms LED chips and diodes interchangeably.
In lighting terms, directional lighting typically refers to light fixtures that can be adjusted and pointed in a specific direction, and often with a narrow beam angle to create a spot light. Many of aspectLED’s recessed fixtures have adjustable heads and customizable beam angles and work well as spot lights for highlighting specific features like artwork.
A driver takes an LED fixture’s specified and rated input voltage (typically a standardized increment like 12VDC, 24VDC, or 110VAC), and converts it to the specific voltage needed to run that particular LED fixture. Drivers typically come with the fixture and must stay with that specific model – they are designed and developed for that application so using them with a different light will often cause poor performance, premature failure, or a range of other issues – even if it’s the same wattage.
Power Supply
Power supplies are commonly used for low voltage scenarios when your supply voltage doesn’t match the fixture’s rated voltage. For example, if using a 12VDC or 24VDC fixture or flexible strip light in a house (which typically runs on 120VAC), it’s necessary to use a power supply to step that line voltage down to the usable low voltage matching your product. Often that means it may be necessary to use both a power supply and a driver. Power supplies do not come with fixtures and must be purchased separately.
Transformers simply transform a voltage down to a specified level. Since power supplies and drivers both transform voltages (albeit to different levels), they are both technically transformers. While we don’t internally call anything a transformer, for many of our customers, transformers, drivers, and power supplies are terms that are used interchangeably despite having slightly different use cases and purposes.
Typically referred to in energy terms, this is how much energy a fixture consumes relative to the amount of light it outputs. While incandescent and halogen bulbs were inefficient and used large amounts of energy, LED replacements often use up to 80% less energy. Some of our recessed LED fixtures and ultra-thin recessed fixtures are rated for equivalent light output to a 65W incandescent bulb – while only using 9 watts.
Foot candle
Foot-candles are yet another unit of measurement for light. A foot candle is specified as the amount of light from a candle that falls on a surface 1 foot away, which means 10 foot candles would be the equivalent light of 10 candles, 1 foot away. This is often abbreviated fc.
Full cutoff
Full cutoff is a style of housing typically used for industrial fixtures like wall packs. These types of housing have reflectors on all sides except the bottom, which directs all light down to illuminate directly under the fixture. Some jurisdictions encourage use of full-cutoff fixtures when possible as a method of reducing light pollution, often in larger metropolitan areas.
Heat dissipation
How a given product handles the heat it generates. LED products are known for generating far less heat than incandescent equivalents, but heat management is still a concern – in some situations more than others. One method of managing thermal performance is by using heat sinks that absorb, direct, and dissipate the heat the fixture produces.
Heat sink
Heatsinks are the assembly that conducts and transfers heat from the fixture to keep the luminaire from overheating. All of our recessed fixtures come with integrated metal heat sink mechanisms and that’s what allows many of our fixtures to be IC Rated for direct contact with insulation.
High power LEDs
LED chips vary in power consumption and output. While some chips like the “on” indicator on your oven are often very simple and low draw LEDs because they don’t need to be super bright, many of our SMD and COB chips are higher output – ranging from 3W per chip all the way up to as high as 50 to 100W per chip. That’s how we’re able to make some of our fixtures in different brightness while having the exact same physical design and housing – by using higher power LEDs.
High intensity discharge
HID lamps are a lighting technology that uses high voltage to send an electric arc between two electrodes (usually made of tungsten), through a tube full of a noble gas. The benefits over incandescent bulb is that it’s substantially brighter while maintaining even light distribution and no buzzing, they use slightly less power, and often longer lifespans. The downsides are cost, often poor color rendering, delicate construction, poor response to being turned on and off frequently, and wiring (due to the need for a ballast which sends a large spike of current at startup). LED fixtures have largely displaced HID fixtures due to the fact that they have all of the benefits and almost none of the shortcomings.
High pressure sodium
High pressure sodium, or HPS lamps, create an arc in a tube between an electrode and a sodium-mercury amalgram. HPS fixtures are very common in parking lot, street, and security light scenarios due to their long life spans and high efficiency. They tend to emit around a 2000K color temperature which is nearly amber, and means they have very poor color rendering. Comparable LED street lights, LED parking lots lights, LED shoebox fixtures, and LED wall packs can provide even more efficiency, longer life, more color temperature flexibility, and better color rendering with minimal retrofit work.
Light emitting diode, a method of lighting that uses a solid state chip (transistor) to create light without using harmful gases or a burning (and easily breakable) filament. LEDs use a fraction of the energy of most lighting technologies and are expected to have a much longer lifespan, while having great color rendering and infinite color temperature flexibility.
LED array
Multiple LEDs combined in one product or fixture form an array. Often an LED array is referred to as all of the LEDs mounted on a single printed circuit board.
Lumens/Luminous Flux
The amount of light emitted from a source. Unlike measurements like foot-candles or lux which measure the light the lands on a surface, a single lumen measures the amount of light a single candle produces in all the directions it shines. A typical incandescent 65 watt bulb produces around 800 lumens, and you can view.
Lumen depreciation
The amount of luminous flux lost over time. Most light sources lose some brightness over their lifespan, and aspectLED fixtures’ 50,000 hour rated life is determined by factoring lumen depreciation to find fixtures’ useful lifespan. That means you can expect aspectLED fixtures to retain at least 70% of their original intensity after 50,000 hours.
Lumen maintenance
Compares the amount of light produced by a luminaire when it was new against what it produces at a specific point in the future. This measurement compliments lumen depreciation.
another term for a light fixture. Often with LEDs, if the product comes with a driver, the term luminaire will refer to the fixture itself.
A unit of measurement for light falling upon a surface. This is simply an alternative to foot candles – while foot candles uses a square foot, 1 foot away from a candle, lux uses 1 square meter, 1 meter away from a candle. Foot candles is more commonly used in the US, while lux tends to be more popular in other countries that are more reliant on the metric system.
Metal halide
Metal halide is a type of high intensity discharge (HID) lamp that uses a mixture of vaporized mercury gas and metal halides to ignite an arc and produce light. Metal halide lamps have existed almost exclusively in industrial settings for flood lights and other areas where high output is needed. LED technology lasts longer, is more robust, less hazardous, and more efficient than metal halide so it has become the de-facto choice for high output flood lights.
A light shining upward, usually to highlight features such as statues, walls, pillars, landscaping, or virtually anything else. Common fixtures used for up lighting include landscape lights, wall washers, flexible strip lights, and in-ground fixtures.
A synonym for recessed fixtures, downlights are typically a standard ceiling recessed light pointing downward.
Useful Life
As LEDs have slight lumen depreciation through their (incredibly long) lifespan, useful life is simply the length of time the fixture performs above a set threshold of its performance – usually 70%. LED fixtures will not simply stop working once they go past that useful life – instead, they will just continue slowly depreciating in lumen output.
The amount of potential energy between points on any given circuit, as opposed to amps/volts which is a measure of electrical current flow. Popular voltage increments include 12VDC, 24VDC, 90-120VAC, 220-240VAC, 277VAC, 347VAC, and 480VAC.
Ambient lighting
Also known as general area lighting, this is just a comfortable level of illumination in a normal room. It is typically bright enough to be able to do most tasks with good safety and visibility, while not being as bright as task lighting.
Usually required for other lighting technologies like fluorescent/CFL, HID, sodium vapor, and other similar technologies. Ballasts are normally mounted externally, which is why some people incorrectly refer to LED drivers as ballasts.
Beam angle
The angle at which light comes out of a fixture. All light fixtures have beam angles and many of aspectLED’s fixtures allow them to be specified to order. Beam angles are important to consider when
Can light
A term typically used as a synonym for recessed fixtures. A can refers to the can shaped housing that accompanies traditional recessed lights which is used to keep high temperature incandescent and halogen bulbs from touching heat sensitive materials like insulation.
Recessed light
Any fixture that is recessed into a surface, whether recessed in-ceiling, in-floor/in-ground, or in-wall. Traditionally, recessed lights have been mostly limited to ceilings and referred to as cans, pot lights, or high-hats. Most aspectLED recessed fixtures are designed to be can-free while still being IC Rated for direct contact with insulation.
Bulb base
Not to be confused with the bulb’s shape and size, the bulb base is the base and connection on a light bulb. These can range from traditional screw bases like E10, E12, E26, E27, E39, and E40 to twist and lock bases like GU10. Many bases were designed for incandescent bulbs but have been adapted for CFLs and LEDs. Additional pin, bi-pin, and plug in style bases often have dozens of variations with small differences. Be sure to verify your model’s compatibility before purchasing a new bulb.
Bulb Shape/Size
Bulb shapes and sizes are independent of the base/screw type and determines the beam direction/reflector, angle, fitment, and aesthetic style of a bulb. Standard lightbulb sizes are typically A19, but other popular options include MR bulbs, G (globe) styles, PAR reflectors, linear fluorescent, and compact fluorescent coils. Some of these have direct replacements while some (like CFL coils) are a byproduct of the lighting technology being used.
The most popular residential screw type bulb base that has been in use for over a hundred years. The contact on the bottom tip is hot (line), and the screw threading is neutral.
Flood light
Wide beam, high brightness light sources, whether fixed or portable. Flood lights are commonly used for stadium lighting, or for industrial settings like construction, production, or any other application where high light intensity and reliability is paramount. Metal halide lamps have traditionally been popular for flood light settings, but LED offers even more light output with lower power use and far longer lifespans.
Compact Fluorescent Lamp – a lighting technology with energy savings over incandescent and halogen fixtures. CFLs are being phased out in favor of LEDs due to their mercury content, flickering, color temperature, dimming challenges, slow warm-up, and buzzing.
Luminous Flux
Another term for the amount of lumens a light source produces. The luminous flux of a standard 65 watt bulb is around 800 lumens.
A common type of twist and lock bulb base.
In lighting, incandescent typically refers to something that emits life as a result of heating a filament. The filament essentially glows and burns due to the electrical charge passing through it. Thomas Edison invented the incandescent light bulb over a hundred years ago.
Kelvin/Color Temperature
Kelvin is a scale and unit of measurement for determining color temperature, or the shade of white from a light source. Generaly, the light spectrum for most uses goes from 1000K (candle light, nearly red) all the way to 9000K which is a blue sky. Our standard color temperatures range from Warm White (3000K, or an incandescent equivalent) all the way to DayWhite (6000K, which is a pure white with almost a slight hint of blue). Color temperature preferences vary by person and by setting, but for most people, a 3000K or 4000K option works best in residential settings.
MR / Multifaceted Reflector bulb
This is a bulb shape that became popular with halogen lighting technology. They are comparable to PAR style bulbs in their reflector and light distribution, but are generally smaller (under 2” in diameter). The most popular size is MR16.
PAR / Parabolic Anodized Reflector
A reflector designed to output light to the front of the bulb. These are most popular in recessed, outdoor, or otherwise shielded fixtures that benefit from having all of their light pointed downward as opposed to omnidirectional style A19 bulbs. Typical sizes are PAR20 and PAR38, and they commonly use incandescent, halogen, CFL, or LED lighting technologies.
The method of changing an old style bulb or fixture for a newer upgrade of some sort, typically with minimal modification required. While a simple LED replacement bulb can be considered a retrofit, it usually refers to slightly more specialized solution designed to interface with older technology. We stock standard recessed fixture retrofit kits as well as industrial retrofit kits designed for high output street lights, wall packs, and more.
RGB is a color changing mechanism that uses 4 separate connections to the fixture – a red negative, a green negative, a blue negative, and a common positive. Each of these can be supplied voltage to produce that color, and mixing colors together and dimming colors individually can produce any of about 16 million color combinations. We carry a full line of RGB flexible strip lights, RGB recessed lights, RGB underwater fixtures, RGB in-ground fixtures and more. We also carry controllers to operate the color changing functionality of these fixtures.
RGB+White is the same as RGB, but typically with included dedicated white LED chips alongside the color chips. That means you can have any color combination you would like, but also have the ability to turn on and off the dedicated white chip(s) independently. This offers more general level or task lighting capability than standard RGB fixtures would provide. We carry RGB+W recessed fixtuers, RGBW underwater fixtures, and more, and also stock RGBW controllers.
Similar to RGBW, except with dedicated amber chips instead of white. They are controlled in much the same way. Most of our RGBW fixtures can be custom ordered with amber instead, contact us for details.
Restriction of Hazardous Substances. This is a regulation that restricts substances like lead. In the electronics industry, this is particularly common due to some manufacturers still using lead solder.
A certification body that validates safety of electronic components. They have rules and regulations that must be followed to maintain an ETL certification and use the ETL mark.
UL/Underwriters Laboratories
Similar to ETL, UL Listed products are held to a specific standard with regard to the safety of their electrical design and construction. UL also conducts periodic random inspections and enforces traceability on all components being used. Many building and electrical inspectors require UL Listed electrical components to be used in residential and commercial construction.
DLC/The DesignLights Consortium
Tests lighting products for compliance with their performance standards for distribution, color, and longevity. DLC certification is most popular with industrial fixtures like street lights, wall packs, high bays, and other similar applications.
CSA / The Canadian Standards Association
A nonprofit mainly concerned with the Canadian market. They test products for compliance with Canadian Electrical Code, engineering standards, and electromagnetic capability.
A mark that declares conformity with certain regulations specified by the European Commission These regulations are mainly concerned with EU health and safety in home and workplace environments.
Surface Mount Diode LEDs are a type of LED that mounts on the surface of a printed circuit board (PCB).
Spotlights are simply a light source with a tightly focused beam angle, typically 15 degrees. This is ideal for highlighting specific features, artwork, or areas from a distance. Spot lights are normally an alternative to traditional flood light or wider beam angles that are used for general area lighting. Many aspectLED light fixtures are available in customizable beam angles.
Troffers are square or rectangular light fixtures that fit into standard suspended or dropped ceiling grids. These grids are typically 2’x2’ or 2’x4’. Most troffers originally used fluorescent bulbs like T8 tube lights. Existing fixtures can be retrofitted to use LED tube lights instead, or entire fixtures can also be replaced with integral LED solutions.
Ceiling panel/panel light
Most panel lights are troffer replacements that have integral LED construction instead of T8 tubes. They often have better light output with longer life, no buzzing, less harsh light, no flickering, and more efficiency. They are built with much slimmer designs and can also be hung with sling kits or surface mounted, as opposed to needing to be used only with a suspended ceiling grid. Another alternative to suspended ceiling panel lights are our Ultra-Thin recessed range.
Ultraviolet (UV)
A wavelength between 10nm and 400nm which is not shorter than what is visible to most humans. While some wavelengths can cause sunburn and even skin diseases, moderate exposure poses little risk, and some wavelengths can actually be beneficial. Ultraviolet lights have many popular uses including entertainment as black lights, counterfeit currency detection, forensics, sanitation, purification, sterilization, and more.
Infrared (IR)
A wavelength between 700nm-1mm, or just longer than the visible light spectrum, on the opposite side of Ultraviolet. Infrared light is commonly used for communications, meteorology, night vision, thermography, and other various forms of imaging. Unlike Ultraviolet light which usually is visible as a dark purple light, infrared is not visible at all and can only be seen by the human eye through a camera.