Now you know your LEDs from your fluorescents, it’s time to dig a little deeper into the terminology used within the lighting industry.


Kelvin is the measurement of light temperature. The lower the temperature the redder the light; the higher the temperature the bluer the light emitted. This is why candle light, at 2000 Kelvin has the soft yellow hue and LED lights are a clean white at 4000 Kelvins.

Typically all Constant Lights are in the 4000 Kelvin mark, meaning they produce a clean, uncoloured white light. We’ve put together a simple chart to show you how Kelvins relate to each other:
Kelvin Chart by Constant Lighting

KelvinsLook out for our colour index/Kelvin icon on each of our products. It will show you clearly the Kelvins of that lighting product.

Colour Rendering Index

Time to get a little technical now. Colour rendering index (CRI) is the term used to rate the ability of a light source to successfully illuminate an object to the levels of natural light as possible. The higher the CRI value the more accurate the lighting replication.

A CRI of 100 would mean the light is identical to standard daylight. Therefore most lighting sources are less than 100, such as LEDs which typically sit at, or greater than 80 on the colour rendering index.

To put LED CRI in perspective, fluorescent lighting will have on average 51-70 CRI rating depending on the lighting method within the fluorescent tube. Therefore LED is a great light source for environments where accurate lighting colours can be vital, such as photography studios and medical environments. More and more production assembly units are using LED light fittings generally to provide better lighting conditions especially where inspection is required.

Here is a photographic replication using our factory of how lighting can affect the colour rendering of objects.
Colour Rendering Example

Colour Rendering IndexWe’ve placed a small icon on all our products to show the CRI of that product.


We’ve gone over Kelvin as well as the Colour Rendering Index (CRI), so the last piece of the terminology puzzle is Lumens (lm).

Traditional light bulbs are rated by watts, and this gave you a good indication, albeit wrongly, of how bright that bulb would be. With LEDs we don’t use watts to indicate light levels, but the more accurate term lumens (lm).

So what are lumens? Lumens are the measure of the total visible light emitted by a source. Constant Lighting’s LEDs range from 2,700 to 24,000 lumens depending on the LED application.

LumensNext to all our products there will be a lumen number, so you know how bright that LED light will be.

Remember, some Constant Lights have a very bright lumen rating as lights in some of our range are suitable for high-rise and applications such as factories where light has to travel further to have an impact i.e. 20ft from ceiling to factory floor.

IP Rating

Ingress Protection (IP) is the effectiveness of a product to exclude the elements such as dirt and water. Each IP rating is made up of two numbers, with the first relating to solids, and the second to liquids.

The term waterproof can be quiet ambiguous, therefore an IP rating was introduced to give a clearer understanding of a products effectiveness to deterring dirt and water.

Depending on the application of the LED lights will depend on the IP rating. Those designed for manufacturing environments may have a rating of 40 or greater. Those for standard office environments would have a typical IP20 rating as it would be rare for them to come into contact with water jets, or have dust clouds surrounding them.

A simple guide to IP ratings
Using the guide below, IP20 would mean a lighting unit has a solid rating of 2 (>12.5mm protection) and a liquid rating of 0 (no protection).
IP Rating Table

IP RatingKeep a look out for this icon as it indicates the IP rating of that product.


An LED light’s brightness is not determined by its wattage. A traditional bulb also isn’t, but we’ve come to associate wattage with brightness. Wattage simply conveys the power required for the light to illuminate. Lumens are the true measure of brightness.

Low wattage consumption is one of the key benefits of LEDs over traditional and fluorescent ones. A typical fluorescent tube will consume 71W of power to produce 3380 lumens of useful light. To achieve the same lumen output with LEDs you will only need 28W of power. A substantial energy cost saver as well as improving your company’s carbon footprint at the same time.

WattageYou can easily see the wattage used per product with our handy icons labelled on each product page.

Kelvin Lighting Guide

Lighting Guide PDF

You can download our handy Kelvin Chart Guide to help guide your operational team in switching to LEDs.