Common LED Terms and Definitions


Metric measurement of how much light is coming from a light source. One Candela is equivalent to the light output of one candle, based on metric calculations.


Stands for Chip On Board Light Emitting Diode. An LED chip diode bonded directly into a cicuit board. Like SMD chips, COB chips can have multiple diodes, but unlike SMDs, COBs have only one circuit and two contacts for entire chip.

High Power COB-LED with low current at 5pct

An example of a COB LED module with 40 single blue power LEDs below the yellow surface

Color Temperature

Also known as CCT — Correlated Color Temperature, refers to the color of light produced by a light source and is measured by the Kelvin temperature scale. Warm light is thought to be friendlier and cool light more business like.

chart showing Kelvin temperatures and equivalent mood and daytime sunlight quantities


A diode allows an electric current to pass in one direction, while blocking current from going in the opposite direction.


Stands for Dual Iinline Package and even though it has been around for over 50 years it is still used for large signs and displays. These pill or button shaped LEDs have two connecting pins that can be be soldered or through-hole mounted to printed circuit boards. Each bulb usually has only one color, though there are RGB LEDs that can show any color, but they cost more and tend to be larger than SMD LEDs. The advantage of using DIP LEDs is that bulbs can be replaced individually and they are great for longer viewing distances. To get multiple colors, DIP screens have red green and blue diodes grouped together to form pixels. Some will have an extra red LED to form a square pixel from 4 lights.

LED, 5mm, green (en)

Drawing of 5mm green DIP LED


Image of an RGB DIP LED

Foot Candle

A measurement of illuminance, equivalent to the the amount of light produced by one candle at a distance of one foot (equal to one lumen per square foot to 10.764 lux). Measurement of light at an illuminated object.

graphic image of a candle one foot away from a board measuring 1 foot tall by 1 foot wide

Heat Sink

Draws heat away from the LEDs to keep them cool, which can increase the lifespan of the LEDs.

image of a TL Energy downlight that has a heat-sink at the base of the light

A TL Energy LED downlight that has a heat-sink at the base of the light


Stands for Light Emitting Diode. Most simply defined, an LED is a semiconductor device that lights up when an electrical current is passed through it. LED lighting uses one or more LEDs as the light source. Compared to incandescent and fluorescent light sources, LEDs have lower energy consumption, last longer, have greater robustness, are smaller in size and are able to light up faster.


LEDs are energy, cost efficient, and they look great. Here are some interesting facts about LEDs that you might not know:


Average hours LEDs last. Newer LEDs double that!

Nearly 95%

Amount of LED that is recyclable, and no mercury!

$265 Billion

Savings over next 20 years if LEDs widely used in US


More energy converted to light than traditional bulbs


A measure of the total quantity of visible light emitted from a source. One lux equals one lumen per square meter. The metric equivalent of foot-candles. Metric measurement of light at an illuminated object.

Chart that compares incandescent, CFL and LED bulbs and watts needed to achieve similar lumens

Luminous Efficacy

A measurement of how well a light source produces visible light. Lumens per watt or lm/W.

Luminous Efficacy chart — info from Energy.gov

A comparison of Luminous Efficacy of different light sources — info from Energy.gov


Measures illuminance or light intensity; the measurement of actual light available, in metric units, at a given distance. One lux equals one lumen per square meter. A light that has high lux output will travel farther but have a smaller spread (like a spot light) whereas a light with low lux output will travel a shorter distance but have a higher spread (like ambient lighting).


Candela output per square meter. A measure of brightness or luminance emitted from an LED Display.


Stands for Out Of Home. Refers to advertising that reaches consumers while they are out of their homes.

image of an OOH LED display on the side of a building

Example of an OOH LED display on the side of a building

Operating Life

Refers to durable light quality of an LED, or length of time that an LED will consistently shine at the expected luminous flux (measure of the total amount of light that a lamp puts out). The following conditions can shorten the operating life of LEDs:

  • Temperature: High heat shortens the life of the LED. It is important, where possible, to direct heat away from the LED.
  • Mechanical: Improper handling during manufacture, assembly or during operation can have a negative affect on the life of the LED
  • Power Consumption: LEDs and LED modules have specific current ranges in which they can safely operate
  • Light: The reflective housing of the LED can in some cases age the LED
  • Dampness: If connections and / electronic parts inside the LED module get damp, they can corrode
  • Chemicals: Corrosion due to high sulfur, salt or chlorine, or exposure to industry chemicals can corrode the LED

Operating Temperature

High temperature is the enemy of LED performance and can shorten the life of LEDs. Many LEDs have heat sinks to draw heat away from the lights. Most manufacturers state optimum operating temperatures for their LEDs.


Stands for Printed Circuit Board. A board made of material that does not conduct electricity — like fiberglass or plastic. Copper or some other metal is etched or set in thin lines inside or onto the surface of the board to make electricity only travel where it is wanted. Electronic components are then attached to the board using a metal. The etched metal enables electricity to travel from one component to another.

Bga und via IMGP4531 wp

Wikimedia Commons — Sliced side view of a printed circuit board


Defined as the distance in millimeters from the center of one pixel / LED cluster to the center of another pixel / LED cluster. The closer the pixels, the closer the viewing distance. Smaller pixel pitch means more LEDs in a display, greater detail and potentially a greater cost. If the display is going to be viewed at a distance then the pixels can be spread farther apart and still give create a nice picture.

graphic showing different variations of pixel pitch

Different variations of pixel pitch


A pixel is one point of a picture. It may consist of one LED or a cluster of LEDs, depending on the sign type. Monochrome displays use only one color of LED while full color displays require a minimum of one red, one green and one blue LED to create one pixel of color.

graphic showing different variations of pixels


The number of pixels present in the physical area of an LED display. The greater the number of pixels in the display the greater the detail of the image being shown. The resolution of a display is determined by the overall display size, the type of pixels used, the pixel pitch and the viewing distance.

image of led diplays on side of building at night

Outdoor displays can often have lower resolution than indoor displays, because viewing distance is farther away


Stands for Red, Green, and Blue. Mixing these three colors in varying intensities can produce a wide gamut of colors. LED color displays use either clusters of red, green and blue DIP LEDs, RGB LEDs, or SMD 3in1 LEDs to produce full color images.


LED chips mounted on the surface of a printed circuit board. Rather than being bullet shaped like a DIP LED, SMD chips are flat square shaped. They can have red, green and blue colored diodes in each chip (3in1) like the 5050 SMD LED chip in the image below. SMD LEDs tend to have wide viewing angles and great color blending at close distances.


Wikimedia Commons — Comparison of SMD LED Modules on light strips, some are (3in1)


Stands for Solid State Lighting. Uses light emitting diodes as the source of illumination, as opposed to electrical filaments (incandescent), or gas (including fluorescent, neon, sodium vapor). Solid state lighting has greater resistance to shock and vibration, and typically lasts longer than conventional or fluorescent lamps.

T8 Bulb

LED version of Fluorescent tube lights. Lasts longer and is better for the environment.

image of an LED T8 tube light that can be used instead of a fluorescent tube light

LED T8 tube lights.

View Angle

Maximum angle at which a display can be viewed with acceptable visual quality. The range of acceptable viewing angles is called the viewing cone. Outside the view angle, images might seem blurry or have poor contrast.

graphic explaining vertical and horizontal viewing angles for LED displays

Viewing Distance

Refers to how close one needs to be to view the content on an LED Display.

graphic showing viewing distances for LED displays

Trans-Lux can help you chose the display that best suits your needs.


A measurement of the rate at which electrical energy is dissipated, expressed as: Power (Watts) = Current (Amps) X Voltage (Volts). LED bulbs require less power (watts) than incandescent or CFL bulbs to produce the same amount of brightness (lumens).