Basic Definitions

1) The luminous flux Φ

Unit: Lumen [lm]
Luminous flux F is defined as the entire light emitted from a light source. A distinction is made here two significant proportions. To explain the difference of the luminous flux for LED.

Sketch: luminous flux up / down

The light stream can be separated into these two components. Most previously used light sources, like traditional bulbs or Neon tubes radiated 360 ​​°.  So the resulting luminous flux is directed upwards and downwards. An LED emits light only in a half-space with a radiation angle of 120°.

2) The light intensity I

Unit: Candela [cd]
Part of the luminous flux radiating in a particular direction

3) The illuminance E

Unit: Lux [lx]
Illuminance E is the ratio of light flux on an illuminated surface.
The illuminance is 1 lx when a luminous flux of 1 lm impinges uniformly on an area of ​​1 square meter.

4) The luminance L

Unit: candela per square meter [cd / m2]
The luminance L is the brightness impression that the eye has from a luminous or illuminated surface.

5) n is the light output

Unit: lumens per watt [lm / W]
The luminous efficacy indicates with which economic efficiency, the electrical power consumed is converted into light.

If you have understood our explanation, good.
If not, we have not explained it simple enough. That’s not your problem but ours. Please let us know.

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