When measuring the brightness and output of a light bar or driving light, there are two common numbers that are used to help understand a lights brightness – Lumens and Lux.
While these ways of measuring light are related, they are not interchangeable – and represent different ways of looking at the brightness of a light. It can seem a little confusing – but we’re going to look into the difference…
What do they mean?
While both lumens and lux measure light, they do so in different ways. Let’s start by looking at the definition of each term:
Lumens – The measurement of light emitted by a bulb. It only looks at the light source.
Lux – Measures a surface illuminated by the light. It considers different factors such as distance from the light source and the direction of the light.
So they both look at light output, but they do so in different ways. A good way to understand the difference is to think of some real world situations:
Lumens
Imagine you have a lit light bulb, and you place it in a shoebox – the bulb is going to fully illuminate that space with lots of light. Now if you take that same bulb and place it in the middle of a dark warehouse, the same bulb isn’t going to light up very much at all. The lumens are the same, but the impact of the light is altered by environmental factors.
Lux
Lux measures the amount of light on a surface – so if you shine a torch at a wall from 1 meter away, it will illuminate the surface. Move back 5 meters, and it will still be illuminating the wall, but it will be much dimmer. The torch itself hasn’t got any dimmer, but the light is being spread further around the room, meaning less light is hitting the surface of the wall. Now if you shine the light through a tube at the wall, you’ll see that less light is escaping into the room, and the surface is brighter.
So the lumens of the torch are the same, but the Lux has increased – One lux is equivalent to one lumen of brightness per square meter – so over a space of one meter squared, a surface with one lux is as bright as a bulb giving off one lumen at point-blank range.
Why lux is an important measure for driving lights?
Lux is important when looking at driving lights as it shows you how effective the source is at lighting the way. You want a light that is excellent at illuminating the way ahead (the lux) and the brightness at point blank range (the lumens) is not so relevant. A good way to think about this is the lux is the distance at which you can be away from the light source, and still have enough light to read a newspaper – so 1 lux at 1km means that at 1km away from the source, there will be enough illumination to light up the newspaper.
How are they related?
When it comes to driving lights, lux is arguably the best measurement to look at, as it gives you more of a real-world idea of how they will light up the way ahead. However, typically a higher lumens rating will directly impact the lux – a brighter light generally goes a further distance. While this isn’t always the case, the way we design our lights gives you optimum lux for the lumens – in other words, we can get excellent range on our lights from less lumens, meaning they are more efficient.
We make it easy by giving you both measurements!
Here at Ultra Vision, we make it easy by giving you both Lux and lumen measurements on our lights. This way, you can see how powerful each model of light is at source AND how this converts into the more helpful measurement of how effective that power is at a distance. By using these numbers, you can get the perfect light for your particular area – driving a lot in built up areas? Then maybe the lumen and lux measurement can be lower, as you won’t need to see as far ahead, and can avoid glare off of road signs or dazzling other drivers. Heading out into the bush with nothing for miles around? Perhaps you want the maximum lumens and lux that we offer to help light the way!