Lumens, Lux & Efficacy

Lux Level Chart
LED Efficacy
LED Efficacy

What are lumens?

The total light output from a light source, regardless of the direction the light travels, is specified as lumens (lm), where 1 lumen is defined as equivalent to the light output from 1 candle. This figure is used to describe and compare lamp brightness.

What is efficacy?

Efficacy (lm/w) is the total light output in lumens per watt of power consumed. The higher the lumens per watt, the more efficient a light source is. The efficacy specification is simple to calculate. For example, a LED globe that produces 720 lumens from 10 watts has an efficacy of 72 lumens per watt (720 lumens/10 watts).

How efficient are LED lights?

The following table shows the power consumption of a LED light is typically 80% less than a halogen of equivalent brightness:

A Comparison of Light Types

Power Output Efficacy
Incandecent 60 watts 770 lm 13 lm/w
Halogen 50 watts 750 lm 15 lm/w
CFL 11 watts 740 lm 65 lm/w
LED 10 watts 720 lm 72 lm/w

 

What is lux?

Lux (lx), is defined as the amount of light arriving at a surface that is a given distance from the light source. 1 lux is equivalent to 1 lumen per square meter, so if you measured 800 lux at 1.5m height using a lux meter, then there is 800 lumens of light per square meter at 1.5m.

Lux Level Chart

 

What lux levels are required for various tasks?

According to the Australian Standard recommendations:

  • General Tasks
    • Reading, Writing – 320lx
    • Background – 160lx
  • Screen Based Tasks
    • Keyboard – 160lx
    • Reference Material
    • Simple – 240lx
    • Average – 320lx
    • Fine – 600lx
    • Background – 160lx
  • Office Area
    • Drawing/Artwork – 600lx
    • Simple Reference Material – 320lx
    • Fine Detail Material – 600lx
    • Background – 240lx
  • Reception Area
    • Enquiry Desk – 320lx
    • Lobby/Foyer – 160lx
  • Meeting Room – 320lx
  • Conference Room – 240lx

 

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