Providing the proper amount of light for a task is vital and impacts safety, productivity, and efficiency. The appropriate light to illuminate a job or process may vary by application.
For measuring the brightness of a light bulb, mainly, two metrics are used widely- Lux and Lumens. These two metrics are related to intelligence but have some distinct characteristics.
- Lux measures the amount of light falling on a surface, while lumens measure the total light output from a light source.
- Lux considers the illuminated area, whereas lumens focus on the brightness of the light source.
- A larger surface area receiving light will have a lower lux value, even if the same amount of lumens is emitted.
Lux vs Lumens
Lux is a unit of measurement that measures the amount of light reaching a surface, defined as one lumen per square meter (lm/m²). Lumens measure the total amount of visible light emitted by a light source, regardless of whether it falls on a surface. They can be used to compare the brightness of different light sources.
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Lux refers to the SI unit of illuminance, which measures luminous flux per given area. It is used for measuring the brightness of light spread on a surface, generally a floor or wall, in a lighting setup.
One Lux is equal to 1 Lumen/m². Lux is used for creating a standard that can be employed across several types of usages and buildings,, allowing comparisons of the lighting quality in one installation to another.
Lumens refer to the SI unit of the current of the light. It measures how much light emits from the light source, generally a light bulb.
The more Lumens a bulb has, the brighter the light is. Lumens are used to measure the brightness of the light in LED lighting. A general 100-watt light bulb outputs 1600 Lumens of light.
|Parameters of Comparison||Lux||Lumens|
|Definition||Lux refers to the SI unit of illuminance that measures the amount of light spread on a given surface.||Lumens refer to the SI unit of brightness that measures how much light is emitted from the light source.|
|Usage||As Lux refers to measuring how much light falls into a surface, a spectrometer or small handheld light meter can measure it.||Lumens are used for determining how much light the light source is emitting.|
|Measurement methods||As Lux refers to a measure of how much light is falling into a surface, a spectrometer or small handheld light meter can measure it.||As Lumens measures the amount of light emitted by the light source in every direction, slightly more sophisticated tools are required to measure it.|
|Relation with Watt||Watts and Lux represent different types of quantities, so converting Lux to Watts is not possible.||One Watt is equal to 12.5 Lumens.|
|Direct sunlight||Direct sunlight has almost 32000-100,000 Lux.||Direct sunlight has 32000-100,000 Lumens/m².|
What is Lux?
The word ‘Lux’ refers to light in Latin. It is a SI unit of illumination which measures the brightness of the light by measuring the amount of light on a given surface.
1 Lumen is equal to one Lumen/m². The square meters expressed the size of the given surface.
It can be calculated from several different ranges of distance. While measuring Lux, you need to be careful about the space.
If two light bulbs with the same Lux are put in different distances, the light bulb in the short length will be more powerful and bright, while the light bulb in the long length will be less optimistic.
The value of Lux in a given space or surface is measured by a light meter. A spectrometer or small handheld light meter can measure it.
While measuring, the light meter needs to be placed at working height. As the distance between the light source and the given surface where the light will spread decreases, the illumination increases in the square meter.
The intensity level of Lux is differentiated in different room setups, a storeroom needs a low level of light. In contrast, an office building where fine work are done needs a high intensity of light.
Generally, 100 Lux is sufficient for illuminating corridors, stairs, and lifts, while 150 Lux is needed for illuminating plant rooms, restrooms, and 200 Lux is needed in lobbies and entrance areas.
Retail spaces, and general office setups need 500 Lux, and more than 500 Lux are only required in pretty unusual circumstances.
What is Lumens?
Lumens refer to the SI unit of luminous flux, which measures how much light a light source emits in all directions. In other words, Lumens measures the amount of light you get from a light source. 1 Watt is equal to 12.5 Lumens.
Fewer Lumens means dimmed light, and more Lumens means brighter light. It is used to measure the current of the artificial lights. It measures the total amount of visible light emitted from a light source./
The total output of Lumens for non-directional bulbs like a candle, globe, or golf ball-shaped light source is measured for all directions.
In directional bulbs like the GU10 spotlight, the light is spread in every direction; in that case, some of the morning or spill light may not be very useful, but it is calculated in total Lumen rating.
To eliminate this issue and get a more accessible and fairer Lumen rating, “useful Lumens” was introduced, a calculation of proper light spread in a standardized ninety-degree cone.
It is generally lower than the total Lumen rating as it eliminates the unuseful lights. But it is relevant while measuring the Lumen rating of a spotlight bulb where the useful light beams are in a forward direction.
Main Differences Between Lux and Lumens
- Lux refers to the SI unit of illuminance that measures the amount of light spread on a given surface. On the other hand, Lumens refers to the SI unit of brightness that measures how much light is emitted from the light source.
- Lux determines how bright a surface appears in a lighting setup. Lumens are used for determining how much light the light source is emitting.
- As Lux refers to measuring how much light falls into a surface, a spectrometer or small handheld light meter can measure it. Slightly more sophisticated tools are required to measure it as Lumens measures the amount of light emitted by the light source in every direction.
- Watts and Lux represent different types of quantities, so converting Lux to Watts is not possible, on the other hand, one Watt is equal to 12.5 Lumens.
- Direct sunlight has almost 32000-100,000 Lux. Direct sunlight has 32000-100,000 Lumens/m².
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.