You just watch that. . . .Beam angle

•December 21, 2012 • Leave a Comment

The more unscrupulous lamp manufacturers out there try a little bafflement to confuse and hide the poor performance of their product but playing with their ‘Beam angle’

Usually the light output is measured with a small hand held light meter (and a small calculation which is dependant on the ceiling height to measured surface). However it is very dependant on where the meter sits in the beam angle as to the result. (For a true measurement an ‘Integrating sphere’ is required, but with these running to £60,000+ for a 2mtr sphere not everyone can afford the outlay)

Lets say that the light meter gives us a measurement of  about 350 lumens at the centre of the beam, the further out towards the edge of the circle of light the less light you will read on the meter. If the lamp has a very small beam angle of say 15 degrees the light will be focused on a relatively small area, and be quite intense. The same lamp spreading its light over a normal 38 degree beam angle would not have the same intensity over the bigger area.

Therefore check the beam angle before you buy, anything around the 35-40 degree beam angle will be similar to your old halogen downlights, if it also gives you 400+ lumens then it might well be the lamp you are look for.


•December 21, 2012 • Leave a Comment

The cost of electricity is measured by multiplying the energy used (In Watts) by how long it is used for (in hours), this is termed Kilowatt-hours or kWh for short. You the consumer is then charged per kWh of electricity you use. Often this is around 12-15 pence per unit but can be more or less depending on how good or bad a deal you have with your energy supplier.

This could be a 1kW electric bar heater on for 1 hour or a 100W lamp on for 10 hours or a 5W lamp on for 200 hours etc etc

Obviously the lower the wattage the longer the ‘device’ can be on for, for your money.


•December 6, 2012 • Leave a Comment

Like everything in our ‘throw away’ era, LED lamps have a lifespan, this should not get confused with warranty (Sometimes termed Guarantee, although they mean something different, the terms are often mixed up).

With good old light bulbs you knew when they had reached their end of life because they went ‘pink’ (Sound and not colour), then you’d be plunged into darkness only go find the candles for the evening until you could nip to the shops to purchase another. Even with the dreaded fluorescent you’d notice the ends turn darker and then one day it would continue flashing instead of blinking into life. Not so with LED.

LEDs are more like trusty librarians than rock and roll stars, so they just gradually fade away rather than burn out. They suffer what is called ‘Luminous decay’ and the point at which we decide they are no longer as bright as they should be is ‘L70’

L70 is generally accepted to be when the luminous (Light) output drops to 70% of the lamps original brightness. This is not to say that they won’t work after this time only it is likely that the human eye will start to register that things are not as bright as they once were.

This figure is usually measured in hours, so will depend on usage, as to when this will occur in real time. If you only used the light on average 4 hours a day and it had a 35,000 hour ‘L70’ then your lamp would last approx . . .

35000/4 = 8750 days / 365 = 23.9 years

Obviously there are a few other factors like high temperature environments, the quality of the electronic components inside and if you bought the lamp from a guy in the pub called Dodgy Dave or not, but otherwise most of these lamps will out live us.

Colour temperature

•December 3, 2012 • Leave a Comment

Yes, your colour has a temperature, no before you reach for the phone to call a doctor, this is perfectly normal.

OK so what is it. . .

If we go back to our happy childhood days when we switched on our 60W tungsten filaments lamps, we marvelled at the warm comforting glow for almost a heartbeat before we picked up our action man and ran around screaming like a lunatic. No, hmm maybe that was just me then. Well that warm cosy glow is now technically termed as 2700K (The K standing for Kelvin).

While this is great for relaxing at home with, it’s not so great to study a book under for instance. It is much better to have a ‘cooler’ white which will keep you awake (Note ‘Cooler’ but not necessarily ‘Brighter’). So the Kelvin scale gives us the warmth of colour of the light source (Or the lack of it). There are a couple of recognised standard values, these being 2700K (also 3000K) Warm white, 4000K White, 6400K Cool White. The lower you go, the closer to the red spectrum (And eventually Infrared) you get whereas the higher numbers push towards the blue spectrum (And then towards ultraviolet).

The lamps outer packaging should display this information, so you know what you are buying.

But why?

Well think of it this way, you come in from a cold rainy day in the country, its drab outside and got home switch the light on and make a hot drink and relax on the sofa. A 2700K lamp is perfect for this; the light source makes your brain think it is warm and cosy. But if you were on a hot dusty desert road and come to an outback bar, that’s the last thing you want, you’d want a nice cooling effect light like a 4000K or maybe even a 6400K to give that chilled ambience. Follow by a cold beer of course to really cool things down, but hey these are only lamps after all we can only expect so much.

Not the brightest tool in the box?

•November 28, 2012 • 1 Comment

As mentioned before (See Lumens vs Watts 26th Nov 12) we are interested in two key elements of a light source, 1. How much power does it consume (Power in watts) and 2. How much light it produces (In Lumens) for us to complete our daily chores.

Let’s face it we really don’t care if it is the most energy efficient lamp (Bulb) on the planet, if we can’t find the beer fridge in the garage because it produces less light than a firefly we are not going to bother. So as an indication see the chart below which trades off our old incandescent (Tungsten filament) lamps against output in lumens.

My thanks to the American DoE for such a helpful and easy to understand chart.

The US is also several steps ahead of the European Union having a very helpful and easy to understand ‘Lighting Facts’ label. As a consequence of Europe’s failure to copy this it and other legislation it is a dumping ground for many products which just couldn’t cut the grade elsewhere in the world.

At time of writing a decent quality 7-8 watt LED will give about 400lm but be watchful.

To be building control compliant in the UK for domestic use, they have to give at least 45lm/W,  from the above example 400/8=50lm/W. These might take getting used to but can certainly light a kitchen to acceptable levels.

Brightest tool in the box? Probably not but its not far off and with the constant rapid advancement they soon will be!

Oh so that’s what it means. . .

•November 27, 2012 • Leave a Comment

Talking to a friend of mine this evening who is not in the lighting industry, I realised that even though I was trying to write in plain English that I still slipped in terms that weren’t in every ones normal vocabulary. So here are a few terms which you ought to know and I will explain what the mean in greater detail in future blogs;

Lamp = Bulb (is like a taboo word for those in the know in the UK, ‘Bulbs are planted in the ground one stalwart is commonly heard to utter)

LED = Light Emitting Diode, a silicon component

Lamp base = the type which dictates what lamp holder it will fit into (i.e. GU10, GU5.3, GX53, E27, B22 etc)

Incandescent or Filament lamp = ‘Old style’ lamps which have a tungsten filament which a current is passed through. It ‘glows’ and emits light but also heat

Fluorescent = An energy efficient alternative to Incandescent, most commonly it a ‘tube’ format, you see these in workshops and Grandad’s garage.

Halogen = A filament lamp which burns in an inert gas and some iodine or bromine.

Wattage = The power used by a product, power is roughly equal to Voltage x Amperes

CRI = Colour Rendering Index (Will cover later) also expressed as Ra – figure should be above 80

Lamp Life = This is the ‘Average’ lamp life, set 20 lamps running when the 10th fails that is the average, as measured by the industry governing bodies. This is NOT how long each lamp will last. Usually only for Filament. Halogen

L70 = The accepted lifespan of an LED product (Lamp or fitting), the number of hours the product will take for luminous decay to reach 70% of initial output.

Luminous Decay = If you pump electricity through anything for long enough it degrades, this is LED slow demise over time

CCT = Colour Correlated Temperature, measured in Kelvin, it shows how warm or cool the light is. Tungsten filament lamps are acknowledged as 2700K

Lumen = A unit of luminous flux, light output over a given area

Equivalence or Equiv. Watts = LEDs use much less energy, this is the equivalent from a Filament lamp

Lm/W = The amount of lumens out for the energy put in

Load = Amount of power (Watts)

Beam Angle = Angle of light output, some lamps disguise their poor performance by using a small beam angle, the accepted normal is 36-40 degrees, high beam angles would be called a ‘flood’ light

Driver = A step down transformer with a bridge rectifier built in. Lower the voltage from the mains and converts it to DC.

Constant Voltage = Most drivers will deliver a constant voltage to the lamp, if this is so the the current will vary depending on load

Constant current = The other main style of driver, delivering a constant current (Measured in mA), if this is so the voltage will vary depending on load

Dimmable = The product is able to have its output varied

Lens = the optic directly in front of the light source, plays a major part in how the light looks

reflector = helps to ‘push’ more of the light out of the fitting/lamp

Power Factor = The ratio of power in converted to power out. The closer to 1 the better, usually better than 0.8

Cooling system = LEDs don’t emit heat but they do generate it and is often removed by a ‘Heatsink’

ta = Ambient temperature that the product is happy to work in under ‘normal’ conditions, higher temperature may give a shorter lifespan

Payback period = the time taken for the product to save the money it cost to buy it, the shorter the better

Am sure I missed a few so look out for part II. . .

Lumens vs Watts

•November 26, 2012 • 2 Comments

In the Red corner we have ‘Watts’ tried and test method of measuring lamp light output for decades and in the Blue corner is the contender ‘Lumens’ whatever they are?

Yes very soon your lamp packaging (if it doesn’t already) will say wattage somewhere on it and LUMENS in big bold letters somewhere more prominent. So why are they changing it? Is it another European thing like the kilometre or the litre?

You see we have been buying lamps for years based on how much energy they use, and mistaken it for how much light it puts out. How many times have you replaced the light bulb in the lounge and thought damn that’s a bit dull I must have put a 40 watt instead of a 60 watt bulb in. Now following along those lines, you try a 10W LED lamp, GLS replacement. Instantly your brain says it going to be almost dark, it’ll never give out enough light. However it does and will.

What you are actually registering is the amount of ‘Lumens’ that the lamp is giving out. Whereas the GLS filament lamp used 60 watts, most of that energy was lost in the form of low grade heat, only a small percentage was actually turned into light.

Now the LED lamp only uses a fraction of the energy, maybe 8 or 10 watts, but the lumens per watt is much higher than the old style GLS lamp and therefore you are using much less energy to light your home, hotel etc

Look at the label next time you buy and find the lumens per watt (lm/W) the higher the better.