Understanding LED lighting:

It was so much simpler in the old days – the more Watts, the brighter the light! Like everything else, lighting has moved on and LED technology gives us far more control over the brightness, colour and direction of the light emitted from a lamp.

In order to get exactly what you need, there are a few basics you need to get your head around.



We’re talking about shades of white here, rather than Christmas lights.

The light colour we’ve all grown up with at home since the days of candles, gas lights and incandescent light bulbs is a yellowy white often called Warm Light.  In the workplace and in task areas like the kitchen or workshop we usually prefer a whiter light.  The boffins have a scale, measured in Kelvin, and abbreviated to ‘K’ based loosely on the colour of metal as it heats up and goes through yellow to red to blue/white.  In the lingo this is called Colour Temperature and you should have a good idea what ‘K’ you’re looking for when selecting a lamp.

If you’re looking for a nice homely, traditional light colour that you can relax and unwind in then you want to be looking for a lamp offering around 2700K to 3000K which is described as Warm Light.  If you prefer something slightly more modern looking then try 4000K, described as White Light - this is the sort of light temperature given off by traditional Halogen spotlights.  If you really want an ultra-modern, clinically clean look with a sharp white light then go for 5000K.  For an office environment you should be looking for a comfortable bright light around the 4000K to 4500K mark.  The higher the K, the whiter and bluer the light – natural daylight can be measured at between 6500K to way beyond 15000K in clear skies but, for indoor lighting, anything above 6500k is just a bit too much.



The amount of light falling on an area, Lux, is measured in lumens (lm).  We’re used to linking brightness with Watts because that’s how old incandescent bulbs worked - the more power a bulb used (Watts), the more light you got.  With LED lighting you need to look at the lumens – each new generation of LED lights squeezes more light out of less power.  This is measured in lumens per Watt and known as efficacy - it’s a measure of efficiency.  So just because one LED lamp has a higher Wattage than another doesn’t mean it’s brighter, it may be just a less efficient design!  So in addition to knowing what colour temperature you want, you should also know how many lumens you want.

One lumen is the light generated by a candle at a distance of one foot (with a light temperature of about 2000k) – that’s not much use unless you’re talking about a relaxing bath with all the trimmings.  This is probably a more useful reference table:

40W incandescent bulb = 360lm

60W incandescent bulb = 800lm

100W incandescent bulb = 1600lm

32W 4’ T8 fluorescent tube = 2800lm

58W 5’ T8 fluorescent tube = 5500lm

It’s worth noting that when it comes to choosing LED lamps, the light generated is more efficient and more directional so before you reach for the 100W incandescent bulb equivalent, you might want to consider a 75W equivalent rated at around 1200lm – you probably won’t notice the difference.


Beam Angle.

Old incandescent bulbs threw out light in just about every direction and you stuck a shade around it to reduce the light being emitted in directions you didn’t want – very wasteful.  Spotlights are more targeted, emitting light pretty much out of one end of the lamp in a narrow or wide beam depending on whether you’re illuminating an object d’art or lighting a room.  Imagine a circle with a lamp at the centre - 360 degrees would be light in every direction, 180 degrees would be half the circle - all sideways and downwards, 30-50 degrees would be a targeted beam.

LED lamps come in many designs, some throw the light entirely down and sideways (140 - 160 degree beam angle), some are closer to replicating incandescents offering 260 or 330 degree beam angles.  Look at what you’re trying to light – if it’s a traditional table lamp, you probably want a lamp that will shine in every direction; if it’s a ceiling lamp you might only want it to shine downwards and sideways – or maybe just downwards.  With spot lights, do you want a narrow focused beam as mood lighting or to illuminate a specific area, or do you want a wider beam to light a room?

So you should now know what Kelvin, lumen and beam angle you want, it’s time to start your search.


Other stuff you might want to know:

Colour rendering

You might have noticed that bulbs also have a CRI rating – it stands for Colour Rendering Index.  This is a measure of a lamp’s ability to render the colours of an object ‘realistically’ or ‘naturally’ compared with more familiar light sources such as incandescent light or daylight.  Sometimes, when shopping, you need to take an item out into the daylight to really see what colour it is.  You certainly wouldn’t want to choose an outfit under a yellow sodium street light which has a very low CRI!  As a rule of thumb, any lamp with a CRI over 80% will show an object’s colour well.



A light-emitting diode (LED) is a semiconductor device that emits photons or light when an electric current is passed through it.  The particles that carry the current (known as electrons and holes) combine together within the semiconductor material to produce light.

Modern LED lamps use a blue LED coated with phosphor - when the blue light strikes the phosphor some of the light passes through as blue, and some excites the phosphor which then emits its own light — mostly yellow and a little red. The combination of the three colors of light is a white light.

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