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 with 100 lumens therefore gives more light than a lamp with 50 lumens.

Most lamps display a single lumen value. However, some lamps show 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 directed towards a specific surface.

Examples of DLS lamps include:

• 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 (such as a bulb), which emits light in all directions, a DLS lamp has a focused light beam (beam angle).

Non-effective lumens (Raw lumens)

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

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

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

Effective lumens

The effective lumens are the light that is actually useful and reaches the intended surface.

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

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

Effective lumens are therefore the light that falls within the beam angle and truly contributes to the illumination.

The effective lumens are always lower than or equal to the non-effective lumens.

Beam angle

The beam angle determines how the light is distributed.

• Wide angle (e.g. 120°)
  • Wider 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 the light reaches the floor 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 lumens
  • This is the main value
  • Indicates how much light is actually useful
• 360° → Non-effective lumens
  • Total light output of the source

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

Summary

• Lumens = brightness of a lamp
• Non-effective lumens = total light production
• Effective lumens = actually useful 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.