Providing the proper amount of light for a task is vital and has an important impact on safety, productivity, and efficiency. The proper amount of light to illuminate a task or process may vary by its application. For measuring the brightness of a light bulb mainly two metrics are used widely- Lux and Lumens. These two metrics are related to brightness but have some distinct characteristics.
Lux vs Lumens
The main difference between Lux and Lumens is that lux refers to a standardized measurement of illuminance that is used to measure the light output amount in a given surface. Lux calculates the area over which the light or luminous flux is spread. On the other hand, lumens refer to the unit of the current of the light. Lumens indicate the total amount of light emitted from the light source. It doesn’t calculate the area in which the light is spread.
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 to make comparisons of the lighting quality in one building to another.
Lumens refer to the SI unit of the current of the light. It measures how much light is emitting 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.
Comparison Table Between Lux and Lumen
|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||Lux is used for determining how bright a surface appears in a lighting setup.||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 distance. If two light bulbs having the same Lux are put in different distances, the light bulb in the short distance will be more powerful and bright, while the light bulb put in the long distance will be less bright.
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, like a storeroom needs a low level of light, while an office building where fine works are done needs a high intensity of light. Generally, 100 Lux is sufficient for illuminating corridors, stairs, lifts, while 150 Lux is needed illuminating plant rooms, restrooms, and 200 Lux is needed in lobbies and entrance areas. Retail spaces, general office setups need 500 Lux, and more than 500 Lux are needed only in fairly unusual circumstances.
What is Lumens?
Lumens refer to the SI unit of luminous flux, which measures how much light a light source is emitting in all directions. In other words, Lumens measures the amount of light you are getting 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 is the measurement of 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 light or rather spill light may not be very useful, but it is calculated in total Lumen rating.
To eliminate this issue and get an easier and fairer Lumen rating, “useful Lumens” was introduced, which is a calculation of useful 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 is used for determining 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 a measure of how much light is falling 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.
Both Lux and Lumens are related to light and brightness. The main difference between Lux and Lumens is that Lux measures the illumination of a given area or space by the light source, in other words, it measures how much a surface or space is illuminated by a light source. On the other hand, Lumens measures the light source. It determines how much light a light source is emitting in every direction.
Lux differs from the distance between the light source and the surface or space in which the light is spreading, the more distance between these two the dimmer the intensity of the light will be. But Lumens doesn’t depend on the distance as it measures the intensity of light from the light source.
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