365 day returns
on all orders &
When you buy any product from well-lit, you have 365 days to return the product to us for any reason, for a full refund. Thats how confident we are that you will love our products. We do require the products back in their original, un-damaged packaging.
free delivery
on orders over £20
All orders are dispatched via Royal Mail 2nd class which takes 2-3 days (excusing Sunday). Next day delivery can be specified during checkout for £10.
Confused about LED terminology?

Confused by LED Terminology?

When switching from traditional lamps to LEDs, it’s easy to become confused.

There are so many options in the market and each one lists a bunch of information on its packaging. Information, you can’t seem to make head or tail of.

Most people give up and just go for the option that fits their budget. I mean as long as it’s an LED – that’s all that matters, right?

Not quite.

No two LEDs are the same or even equal in quality. If you want to make an informed decision before investing your hard earned money, then you need to know a few key words related to the lighting and in particular, LED industry.


Ambient Temperature

Measurement unit of air temperature in the vicinity of the object, in this case the LED lamp.

Amp or Ampere

Unit of measurement of the quantity of electrical current flowing in an electrical circuit. Similar to amount of water flowing through a pipe.


A non-specific term for the perceived level of illumination – either of a lamp or an object; like hotness or sharpness.

Colour Rendering

Term used to describe the effect an artificial light source has on the colour of an object in relation to natural light.

Colour Rendering Index (CRI)

The quantitative measurement (0-100) of a light source to accurately reproduce the colours of objects compared with a reference light source; 0 is poor 100 is perfect.

Colour Temperature

Measurement of how warm (red) or cool (blue) the light emitted by a lamp appears. Colour temperature is measured in degrees Kelvin (K). The lower the colour temperature the warmer (redder) the lamp and illuminated objects will appear. A rough approximation of lamp classification is:

Warm White – 2700k

Natural White – 4000k

Cool White or True White – 5500k


A translucent material minimizing brighter and darker areas providing an even and consistent dispersion of light from a source


Specialized electronic device used to provide regulated power to an LED.


The total output of a lamp in lumens (amount of visible light) divided by the electrical input power (watts) to give a lumens per watt figure; higher is better.

Luminous Flux

This is the measure of the power of light perceived by the human eye. It is measured in lumens as indicated on the lamp you purchase. It is NOT brightness (see above). If you stand a long way from a light source, it won’t seem as “bright” as closer up. The output of a lamp is fixed, the effect it has depends on the distance from the lamp.


The measure of total luminous flux falling onto a surface unit area; foot-candles (fc) for square feet, lux (lx) for square metres. The further a light source is away from an area the greater the area the source will illuminate but the less energy will fall on each unit area.

Heat Dissipation / Heat Sink

Method used to remove heat away from the critical components of an LED lamp.

Light Emitting Diode (LED)

A semiconductor device that converts electrical energy into light.

LED Chip

Surface mounting LED designed for automated assembly.

Lumen (lm)

The Lumen is the unit of measurement of visible light (luminous flux or power) given off by a light source.

Lumen Decay / Depreciation

This is the measure of decline of output of a light source over the life of the light source.

Luminous Efficiency

Slightly different from Efficiency above, it is a ratio of the luminous flux (perceived power of light) to the radiant flux (total amount of energy emitted from the light source, heat and ultraviolet are emitted but can’t be seen by the human eye).


The International measurement unit of illuminance i.e. light falling on a unit area.

PF Power Factor

The number expressed as the ratio between real power and apparent power in an AC power circuit. The number varies between 0 (least efficient) and 1 (most efficient). Real power is how much power the load actually uses and apparent power is the amount of power that must be generated to power the load. A 10w LED or compact fluorescent lamp with a PF of 0.5 will use and you will pay for 10w but will require 20w to be generated by the electricity supplier; the 10w difference is “lost” in heating up the supply cables. A well designed LED power supply/driver should have a PF of 0.8 to 1.

SMD Surfaced Mount Device

Electronic component, such as an LED chip, without wire connectors, intended for automated assembly on to an electronic circuit board.

Thermal Management

Planned control of the operating temperature of a device either passively or actively.


The unit used to indicate the instantaneous energy used by an electrical device during operation. Volts x amps = watts 1000 watts = 1kW (kilowatt) You pay for how much you use and for how long you use it. Use 1kW for 1 hour and you have used 1kW hour of electricity; you are charged for 1kW hr of electricity on your bill.


There you go. Now you understand enough of the LED industry terminology to make an informed decision when buying LEDs.


In case you don’t understand a term or come across one we haven’t listed, contact us and we’ll be more than happy to help!

Date: 06 Apr 2016