LUX, LUMES and LIGHT BARS

LED Light Bars - The Technical Part

Lamps used for lighting are usually labelled with their light output in lumen which is commonly required by law. For LED Light Bar technology, this way of measuring of light output is quickly becoming standard procedure.  You can find the intensity of light output of the Halo Light Bars, written in our product specifications of all products.

Light history and other fairly pointless facts that you may perhaps find interesting:

1) A 23 watt compact fluorescent lamp emits about 1500–1600 lm.[3][4]

2) On 1 September 2010, the European Union brought in a legislation which stated that all lighting equipment needs to be labelled in terms of lumen instead of how many watts of electricity are consumed by the lamp.

3) Lumen (unit), the SI unit of luminous flux. The lux (symbol: lx) is the SI unit of illuminance and luminous emittance measuring luminous flux per unit area. In photometry, this is used as a way of determining the intensity (as comprehended by the human eye) of light that makes impact with or goes through a surface. It is parallel to the radiometric unit watts per square metre, but with the power at each wave length weighted according to the luminosity function, a standardised model of human visual brightness perception. In English, “lux” is used in both singular and plural.[1]

4) Illuminance is a measure of how much luminous flux is covering a particular area. A good way to think of it, is that luminous flux is a measure of the total amount of light that is visibly present. Illuminance on the other hand, is the measure of intensity of illumination on a surface. It’s not a surprising fact that light will light up a surface less brightly if extended over a bigger area, thus, illuminance is directly proportional to area.

One lux is equal to one lumen per square metre:

1 lx = 1 lm/m2 = 1 cd·sr·m2.

5) A flux of 1,000 lumens concentrated into an area of one square metre, lights up that square metre with an illuminance of 1,000 lux. However, the same 1,000 lumen, spread out over ten square metres, produces a dimmer illuminance of only 100 lux.

Managing an illuminance of 500 lux may be feasible in a home kitchen with a single fluorescent direct light bulb with an output of 12,000 lumen. However, to light up a large space such as a factory floor which has a much larger surface area, would need dozens of these fixtures. So, lighting a larger area to the same level of lux, needs a considerable higher number of lumen.

If you’re still reading this after all the technical jargon, pop a beer cap and give some thought to this:

As with other SI units, SI prefixes can be used, for example a kilolux (klx) is 1,000 lux.

Illuminance in lux.                                                Example
10−4 lux Total starlight, overcast sky
0.002 lux Moonless clear night sky with airglow
0.01 lux Quarter moon
0.27 lux Full moon on a clear night
1 lux Full moon overhead at tropical latitudes
3.4 lux Dark limit of civil twilight under a clear sky
50 lux Family living room (Australia, 1998)
80 lux Hallway/toilet in office buildings
100 lux Very dark overcast day
320–500 lux Office lighting
400 lux Sunrise or sunset on a clear day.
1,000 lux Overcast day; typical TV studio lighting
10K–25K lux Full daylight (not direct sun)
32K–130K lux Direct sunlight