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  2. Luminous intensity - Wikipedia

    en.wikipedia.org/wiki/Luminous_intensity

    Quantity Unit Dimension [nb 1]Notes Name Symbol [nb 2] Name Symbol Luminous energy: Q v [nb 3]: lumen second: lm⋅s : T⋅J: The lumen second is sometimes called the talbot.: Luminous flux, luminous power

  3. Luminance - Wikipedia

    en.wikipedia.org/wiki/Luminance

    A tea light-type candle, imaged with a luminance camera; false colors indicate luminance levels per the bar on the right (cd/m 2). Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. [1]

  4. Light meter - Wikipedia

    en.wikipedia.org/wiki/Light_meter

    Use of a light meter for portrait cinematography in a Turkish music video set. A light meter (or illuminometer) is a device used to measure the amount of light.In photography, an exposure meter is a light meter coupled to either a digital or analog calculator which displays the correct shutter speed and f-number for optimum exposure, given a certain lighting situation and film speed.

  5. Luminous flux - Wikipedia

    en.wikipedia.org/wiki/Luminous_flux

    The SI unit of luminous flux is the lumen (lm). One lumen is defined as the luminous flux of light produced by a light source that emits one candela of luminous intensity over a solid angle of one steradian.

  6. Candela - Wikipedia

    en.wikipedia.org/wiki/Candela

    The 26th General Conference on Weights and Measures (CGPM) redefined the candela in 2018. [10] [11] The new definition, which took effect on 20 May 2019, is: The candela [...] is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of frequency 540 × 10 12 Hz, [a] K cd, to be 683 when expressed in the unit lm W −1, which is equal to cd sr W −1 ...

  7. Optical instrument - Wikipedia

    en.wikipedia.org/wiki/Optical_instrument

    An illustration of some of the optical devices available for laboratory work in England in 1858. An optical instrument is a device that processes light waves (or photons), either to enhance an image for viewing or to analyze and determine their characteristic properties.

  8. Radiant intensity - Wikipedia

    en.wikipedia.org/wiki/Radiant_intensity

    Radiant intensity is used to characterize the emission of radiation by an antenna: [2], = (), where E e is the irradiance of the antenna;; r is the distance from the antenna.; Unlike power density, radiant intensity does not depend on distance: because radiant intensity is defined as the power through a solid angle, the decreasing power density over distance due to the inverse-square law is ...

  9. Visible spectrum - Wikipedia

    en.wikipedia.org/wiki/Visible_spectrum

    White light is dispersed by a glass prism into the colors of the visible spectrum.. The visible spectrum is the band of the electromagnetic spectrum that is visible to the human eye.