What do the terms lux and lumen mean?

Basic information about lighting measurement

If you've ever bought a lamp, you've probably heard the term "lux". But what exactly does this term mean? In this text you will learn everything you need to know about lux and lighting measurements. When it comes to lighting, it is not only the luminaire design that plays an important role, but also the properties of the light itself. 

However, there are countless units of measurement that need to be taken into account - one of which is illuminance. It is measured in lux, abbreviated to lx, which comes from Latin and can be translated as light. In this article, we will explain exactly what this means.

Illuminance is expressed in the physical unit lux and indicates how much light or luminous flux falls on a certain surface. However, this is not the same as brightness, as a white wall, for example, appears much brighter than a dark area with the same illuminance. The color of the surface therefore has an enormous influence on our perception of brightness.

Illuminance is important to ensure that we have enough light to carry out our daily tasks. Too little light can cause eye strain and headaches, while too much light can be blinding. Lux is also important to ensure we have the right type of lighting for our needs. For example, you need more lighting in a workspace than in a living room.

Lux can be measured with a luxmeter, which usually consists of a light sensor and a display unit. The light sensor records the incident light and the display device shows the illuminance in lux. There are also apps for smartphones that can measure illuminance, but they are generally not as accurate as a lux meter. Depending on the room, we recommend different illuminance levels: In our opinion, an illuminance of 100-200 lux is suitable in the living room. Whereas 300 to 500 lux is more suitable in the office. In surgery, a guideline value of 5000 lux should be used.

If you want to make sure that you have enough light for your needs, you can measure the illuminance in lux. For example, if you find that your living room only has 50 lux, you can buy a more powerful lamp or add an additional light source to increase the illuminance.

You won't find any information on the luminaire or light source packaging. How many lux the illuminance of a lamp has must be calculated by yourself, as this depends heavily on the positioning of the luminaire: If it is positioned very close to a surface, the lux value is much higher than if the light source is very far away from the surface. 

Illuminance is now defined as lumens per square meter (lm/m²) and is measured with a so-called luxmeter on horizontal and vertical surfaces or using simulations. In addition to the distance of the luminaire to the surface and the lumen value, the beam angle of the lamp is also required in order to ultimately determine the exact number of lux.

"When buying luminaires, you should make sure that the illuminance is matched to the room. Use warm light in living areas and cooler light in work areas. Smart lamps offer a flexible and adaptable lighting option."

The importance of the terms lux and lumen

Lux and lumen are both units of measurement that play an important role in the lighting of rooms and buildings. While the lumen describes the amount of light emitted by a light source, the lux indicates how much light falls on a certain surface. When buying lights for indoor or outdoor use, it is important to consider both the lumen and the lux value. A lamp with a high lumen rating is not always synonymous with good lighting.

A high lumen rating only means that the lamp emits a lot of light. However, the brightness is influenced by the size of the room and the height of the lamp. A room with a high ceiling, for example, requires a higher number of lumens in order to be sufficiently illuminated. The lux value is an important factor for the illuminance in a room. 

To determine the correct illuminance for a room, various factors such as the size of the room, the ceiling height and the type of activities taking place in the room must be taken into account. For example, a work area or kitchen counter requires a higher illuminance than a living room. 

Choosing the right lighting is not just about considering the right lux and lumen levels, but also the color temperature and color rendering index (CRI) of the light source. The color temperature is measured in Kelvin (K) and influences the atmosphere of the room. 

Warm white light (2700K-3000K) creates a cozy atmosphere, while cooler light (5000K-6500K) is more suitable for work areas.

The CRI is a measure of a light source's ability to reproduce colors faithfully. A high CRI is particularly important in rooms such as bathrooms where make-up is applied or in art studios where color rendering is important. Another important consideration when choosing lighting is energy consumption. 

Lights powered by LED technology generally have lower energy consumption than conventional incandescent or halogen bulbs. LED lights also have a longer lifespan and are more environmentally friendly as they consume less energy and produce less waste.

When installing lights, it is important to comply with safety regulations. Electrical installation should be carried out by a professional to avoid electric shocks or fires. The lights should also be installed in places where they cannot be accidentally damaged, for example near doors or windows. 

Important photometric values

• Lumen: how much light a light source emits per second in total
• Luminous intensity (candela): indicates the current related to the solid angle
• Illuminance lux: luminous flux that strikes a specific surface
• Luminance: provides detailed information about the luminous flux emitted

What other things do I need to consider when lighting my living room?

Illuminance in lux is less relevant for private individuals, but mainly for business and public places, as certain regulations apply here. They serve the purpose of occupational safety and personal safety and should therefore be complied with:

- Workplace lighting: min. 500 lux (the more detailed the activity, the more)

- Traffic zone lighting: 100 lux

- Street lighting: 10 lux

- Escape route lighting: center min. 1 lux

You can also use these guidelines as a guide for your private rooms. Nevertheless, it makes more sense to focus on the luminous flux and the beam angle in order to roughly estimate the illuminance when purchasing. After all, this is not simply stated and requires a calculation first.

- Bedroom: 45 lux

- Living room: 77 lux

- Bathroom: 110 lux

Conclusion - How to do everything right!

Overall, choosing the right lighting is an important factor for the functionality and atmosphere of a room. Taking lux, lumen, color temperature and CRI into account when selecting luminaires can help to find the best lighting solution for the room. 

Current lighting trends, such as the use of decorative luminaires and smart lamps, offer additional options for improving the lighting in a room.

If you're still undecided about how you want to implement lighting in your home, why not make an appointment with the lighting professionals at skapetze®, for a personal consultation and the development of an individual lighting concept lighting concept.

You are also welcome to visit us on site in Simbach am Inn in our light studio come and visit us.

If you already have a concrete idea of what the lights in your living room should look like, we can help you turn this idea into reality - our in-house workshop makes it possible.