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Test Your Knowledge of Lumens

True Or False
  • The word lumen comes from the surname of the French inventors August and Louis Lumière, who pioneered an early version of the light projector.
  • Lumens are used to describe the brightness of both projectors and flat-panel displays.
  • ANSI lumens are brighter than regular lumens.
  • When two projectors are shown side by side, there needs to be about a 30 percent differential in the ANSI lumen rating before the human eye can notice an appreciable difference in brightness between them.
  • One watt of light energy equals about 683 lumens.

Answers

1. FALSE. Lumen comes from the Latin word l3men, meaning an opening or light.

2. FALSE. Lumens are a measure of luminous flux energy emitted from a light source. We use “nits” or candelas per meter squared as the unit of measure for light sources.

3. FALSE. The ANSI standard simply delineates the method for measuring average luminous flux; it is not a different lumen. ANSI lumens are measured using an average of several measurements taken across the face of the light source, attempting to account for brightness uniformity. A brightness specification that is not noted ANSI may be a higher lumens figure, because it may be measured at the source's single brightest position.

4. TRUE. However, a typical 100 watt incandescent bulb has a luminous flux of about 1,700 lumens.

5. TRUE.

Sources: University of Arizona Optical Sciences Center, Georgia State University “Hyperphysics,” projectorcentral.com



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