What are lumens?

Lumens (lm) indicate how much visible light a lamp produces. Simply put: the higher the number of lumens, the brighter the lamp.

A lamp of 100 lumens therefore emits more light than a lamp of 50 lumens.

Most lamps show a single lumen value. However, some lamps display two values. This occurs with so-called DLS lamps.

What is a DLS lamp?

DLS stands for Direct Light Source. These are lamps where the majority of the light is emitted in a directed manner towards a specific surface.

Examples of DLS lamps are:

• Floodlights
• GU10 spots
• High bay lamps
• LED panels

With these lamps, at least 80% of the light actually reaches the surface to be illuminated.

In contrast to a standard lamp (like a bulb), which emits light in all directions, a DLS lamp has a directed light beam (beam angle).

Non-effective lumen (Raw lumen)

The non-effective lumen (also called raw lumen) indicates the total amount of light produced by a lamp at the source.

Example:
A floodlight with 24 LED chips each of 100 lumens has:
24 × 100 = 2400 lumens (non-effective)

This is the maximum light output of the lamp, without accounting for losses.

Effective lumen

The effective lumen is the light that is actually usable and reaches the intended surface.

During the distribution of light, a part is always lost, for example, due to:

• reflection
• glass or housing
• diffusion of the light beam

Effective lumen is therefore the light that falls within the beam angle and truly contributes to the illumination.

Effective lumen is always lower than or equal to non-effective lumen.

Beam angle

The beam angle determines how the light is distributed.

• Wide angle (e.g. 120°)
  • Broader light pattern
  • Larger surface illuminated
  • Less intense light per m²
• Narrow angle (e.g. 90°)
  • More concentrated light
  • Smaller surface
  • Higher light intensity

Practical example

Are you hanging a high bay lamp high up in a warehouse?
Then a narrower beam angle is often better, so that the light reaches the ground in a concentrated way.

Why are there two lumen values on the packaging?

With DLS lamps, you often see two lumen values:

• Φ (phi) → Effective lumen
  • This is the main value
  • Indicates how much light is actually usable
• 360° → Non-effective lumen
  • Total light output of the source

The prominently displayed value (Φ) is therefore what you actually experience as light.

Summary

• Lumen = brightness of a lamp
• Non-effective lumen = total light production
• Effective lumen = actually usable light
• Beam angle determines how the light is distributed

By understanding these differences, you can better determine which lamp is most suitable for your situation.