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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 ), which encompasses all electromagnetic waves emitted, including non-visible ones such as thermal radiation ( infrared ).

  3. 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 ...

  4. Lumen method - Wikipedia

    en.wikipedia.org/wiki/Lumen_method

    In lighting design, the lumen method, (also called zonal cavity method), is a simplified method to calculate the light level in a room. The method is a series of calculations that uses horizontal illuminance criteria to establish a uniform luminaire layout in a space.

  5. Fluorescent-lamp formats - Wikipedia

    en.wikipedia.org/wiki/Fluorescent-lamp_formats

    High-lumen retrofit lamps for 40W T12 lamps in North America. Popular tube diameter in Japan; Circular 32W and 40W T10 lamps (Older versions of the 32W and 40W T9 lamps) T12 T38 1 + 1 ⁄ 2: 38.1 G13 bi-pin; Fa8 single-pin; R17d recessed double contact; One of the first diameters of fluorescent lamps, with the 15W T12 and 20W T12 having been ...

  6. 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.

  7. 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)

  8. Photometry (optics) - Wikipedia

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

    The lumen is defined as amount of light given into one steradian by a point source of one candela strength; while the candela, a base SI unit, is defined as the luminous intensity of a source of monochromatic radiation, of frequency 540 terahertz, and a radiant intensity of 1/683 watts per steradian.

  9. Illuminance - Wikipedia

    en.wikipedia.org/wiki/Illuminance

    Illuminance diagram with units and terminology. In photometry, illuminance is the total luminous flux incident on a surface, per unit area. [1] It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate with human brightness perception. [2]