Lux vs Lumens vs Candela in Bike Lights

Founder, Mr. Mamil
Updated:

When choosing a bike light, brightness is one of the most important factors. The right brightness level will help you stay visible to other road users and allow you to see any potential hazards or obstacles ahead. 

Lumens and lux are two measurement units commonly used to describe the brightness of a bike light, but what do these terms mean, and which one should you pay more attention to?

This article compares lumens and lux and explains why lux is a more accurate measure of brightness than lumens, even though lumens is the more commonly used unit of measurement for bike lights.

Key takeaways

  • Brightness is an important factor when choosing a bike light.
  • Lumens measure the total amount of light emitted, while lux measures the amount of light that falls on a specific area.
  • Lux is a more accurate measure of brightness because it considers the distance between the light source and the illuminated object.
  • The beam angle of a bike light affects both the lux and lumens output.
  • Bike light manufacturers prefer to use lumens as the primary unit of measurement because it gives a higher number for marketing purposes.

Lumens (lm)

Lumens (lm) is a way to measure the amount of visible light that comes from a light source regardless of the light direction, reach, and intensity.

Most lighting companies use lumens to describe how bright their lights are. For example, a bike light might have four LEDs producing 250 lumens each. When all four LEDs work together, the light produces 1,000 lumens. 

The more lumens a bike light has, the brighter it will be. So, if you’re looking for a bike light to help you see and be seen in low-light conditions, you’ll choose a light with a high lumen count.

Lux (lx)

Lux (lx) measures the amount of light that falls on a particular surface area, considering the distance between the light source and the surface. 

Lux provides a more accurate measure of how bright the light appears to a cyclist on the road. 

For instance, if a bike light has a Lux rating of 100lx, the light produces a brightness of 100 lumens per square meter. This measurement considers both the distance between the light and the surface and the size of the illuminated area, providing a more accurate representation of the light’s effectiveness in real-world conditions.

Candela (cd)

Candela (cd) is a measurement unit that describes a light source’s intensity in a particular direction. It is also known as luminous intensity.

Candela is a term commonly used in the lighting industry to describe how bright a light appears from a certain angle or direction.

Candela is different from lumens and lux. While lumens describe the total amount of light emitted by a source, and lux describe the amount of light that falls on a surface per unit area, candela is more specific to the direction in which light is emitted.

While candela can be useful in some contexts, it is not commonly used for bike lights because it does not accurately represent the light’s brightness as experienced by a cyclist.

Impact of beam angle on lux and lumens

The beam angle of a bike light can significantly impact the light’s lux and lumens.

Lumens describe the total amount of visible light emitted by a light source, while lux measures the amount of light that falls on a particular area.

The beam angle of a bike light determines the illuminated area’s size and the light’s intensity, which ultimately affects the lux and lumens output.

A bike light with a wide beam angle will have a larger illuminated area and appear brighter when measured in lumens. A wider beam angle spreads the light over a larger area, producing higher total lumens output. However, this wider beam angle means the light is less focused and less intense, resulting in a lower lux output.

On the other hand, a bike light with a narrow beam angle will have a smaller illuminated area but a more concentrated and focused beam of light. This results in a higher lux output but a lower lumen output. The light will appear less bright when measured in lumens but will effectively illuminate the road ahead at a distance.

For example, a bike light with a wide beam angle of 120º may have a 1,000 lumens output, while a bike light with a narrow beam angle of 20º may have 500 lumens output. However, the narrow beam angle light will have a higher lux output and will effectively illuminate the road ahead at a distance.

Why is lux more accurate than lumens?

Lux is more accurate than lumens when measuring the effectiveness of bike lights because it considers the distance between the light source and the object being illuminated.

Lumens measure the total amount of light emitted by the source, while lux measures the amount of light that falls on a particular area. This means that lux considers the illuminated area’s size and the distance between the light and the area.

For example, a bike light with a high lumen count may appear very bright up close but may not effectively illuminate the road ahead at a distance. In contrast, a light with a lower Lumen count but a higher Lux rating may be more effective at illuminating the road ahead because it has a more focused and concentrated beam.

By measuring the amount of light that falls on a specific area, lux provides a more accurate measure of the effectiveness of a bike light in real-world conditions, taking into account both the size of the illuminated area and the distance between the light and the area.

Why is lumens used instead of lux?

Bike light manufacturers prefer to use Lumens as the primary unit of measurement because it gives a higher number for marketing purposes.

For example, a bike light with a 1,000 lumens output sounds more impressive than one with a 50 lux rating, even if the latter is brighter on the road.

The difference between lumens and lux can be illustrated by considering two bike lights, one with a wide beam angle and another with a narrow beam angle.

The light with the wider beam angle will have a higher lumen output since it emits more light in total. However, the light with the narrower beam angle will have a higher lux output since it is more concentrated and focused, creating a brighter light spot on the road.

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Alex Lee at Mr.Mamil

Alex Lee is the founder and editor-at-large of Mr. Mamil. Coming from a professional engineering background, he breaks down technical cycling nuances into an easy-to-understand and digestible format here.

He has been riding road bikes actively for the past 12 years and started racing competitively in the senior category during the summer recently.