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2. 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) in that radiant flux includes all electromagnetic waves emitted, while luminous flux is weighted according to a model (a "luminosity function") of the human eye's sensitivity to ...

3. Luminous efficacy - Wikipedia

   en.wikipedia.org/wiki/Luminous_efficacy

   Luminous efficacy can be normalized by the maximum possible luminous efficacy to a dimensionless quantity called luminous efficiency.The distinction between efficacy and efficiency is not always carefully maintained in published sources, so it is not uncommon to see "efficiencies" expressed in lumens per watt, or "efficacies" expressed as a percentage.

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. Photometry (optics) - Wikipedia

   en.wikipedia.org/wiki/Photometry_(optics)

   Combining these definitions, we see that 1/683 watt of 555 nanometre green light provides one lumen. The relation between watts and lumens is not just a simple scaling factor. We know this already, because the 60 watt incandescent bulb and the 15 watt compact fluorescent can both provide 900 lumens. The definition tells us that 1 watt of pure ...

6. Luminous efficiency function - Wikipedia

   en.wikipedia.org/wiki/Luminous_efficiency_function

   Φ v is the luminous flux, in lumens; Φ e,λ is the spectral radiant flux, in watts per nanometre; y (λ), also known as V(λ), is the luminosity function, dimensionless; λ is the wavelength, in nanometres. Formally, the integral is the inner product of the luminosity function with the spectral power distribution. [2]

7. Luminous intensity - Wikipedia

   en.wikipedia.org/wiki/Luminous_intensity

   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 intensity of 1 candela. If the optics were changed to concentrate the beam into 1/2 steradian then the source would have a luminous intensity of 2 candela.

8. Luminosity - Wikipedia

   en.wikipedia.org/wiki/Luminosity

   In contrast, the term brightness in astronomy is generally used to refer to an object's apparent brightness: that is, how bright an object appears to an observer. Apparent brightness depends on both the luminosity of the object and the distance between the object and observer, and also on any absorption of light along the path from object to ...

9. Luminous energy - Wikipedia

   en.wikipedia.org/wiki/Luminous_energy

   Here is the wavelength of light, and ¯ is the luminous efficiency function, which represents the eye's sensitivity to different wavelengths of light. Luminous energy is the integrated luminous flux in a given period of time: Q v = ∫ 0 T Φ v ( t ) d t {\displaystyle Q_{\mathrm {v} }=\int _{0}^{T}{\mathit {\Phi _{\mathrm {v} }}}(t)\,\mathrm ...