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2. Candlepower - Wikipedia

   en.wikipedia.org/wiki/Candlepower

   The Germans, however, dissented and decided to use a definition equal to 9/10 of the output of a Hefner lamp. In 1921, the Commission Internationale de l'Eclairage (International Commission for Illumination, commonly referred to as the CIE) redefined the international candle again in terms of a carbon filament incandescent lamp .

3. Lumen (unit) - Wikipedia

   en.wikipedia.org/wiki/Lumen_(unit)

   The lumen (symbol: lm) is the unit of luminous flux, a measure of the perceived power of visible light emitted by a source, in the International System of Units (SI). Luminous flux differs from power ( radiant flux ), which encompasses all electromagnetic waves emitted, including non-visible ones such as thermal radiation ( infrared ).

4. Luminous flux - Wikipedia

   en.wikipedia.org/wiki/Luminous_flux

   Luminous flux (in lumens) is a measure of the total amount of light a lamp puts out. The luminous intensity (in candelas) is a measure of how bright the beam in a particular direction is. If a lamp has a 1 lumen bulb and the optics of the lamp are set up to focus the light evenly into a 1 steradian beam, then the beam would have a luminous ...

5. Guide number - Wikipedia

   en.wikipedia.org/wiki/Guide_number

   Unit: Lumen⋅second Definition: In the context of flash devices, is the measure of the total energy, or quantity, of eye-adjusted visible light emitted over a period of time. In common vernacular, it is the total amount of light released over the course of a flash. Illuminance Symbol: E v Unit: Lux (lumens per square meter)

6. Light intensity - Wikipedia

   en.wikipedia.org/wiki/Light_intensity

   Luminous intensity, a photometric quantity measured in lumens per steradian (lm/sr), or candela (cd) Irradiance, a radiometric quantity, measured in watts per square meter (W/m 2) Intensity (physics), the name for irradiance used in other branches of physics (W/m 2) Radiance, commonly called "intensity" in astronomy and astrophysics (W·sr −1 ...

7. Flashlight - Wikipedia

   en.wikipedia.org/wiki/Flashlight

   Light output from LED flashlights varies even more widely than for incandescent lights. "Keychain" type lamps operating on button batteries, or lights using a single 5 mm LED, may only produce a few lumens. Even a small LED flashlight operating on an AA cell, but equipped with an LED, can emit 100 lumens.