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Comparison of photometric and radiometric quantities. Radiometry is a set of techniques for measuring electromagnetic radiation, including visible light.Radiometric techniques in optics characterize the distribution of the radiation's power in space, as opposed to photometric techniques, which characterize the light's interaction with the human eye.
Luminous intensity (photometric) and radiant intensity (radiometric) In photometric quantities every wavelength is weighted according to how sensitive the human eye is to it, while radiometric quantities use unweighted absolute power. For example, the eye responds much more strongly to green light than to red, so a green source will have ...
2 = any non-empty string other than "self" The template will display a "(Compare)" link (as above). However, the link will point to the corresponding photometry table in the separate article on " Photometry (optics) ", not to within the article, where the {{SI radiometry units}} template has been included.
cd/m 2 (= lm/(sr⋅m 2)) L −2 ⋅J: Luminous flux per unit solid angle per unit projected source area. The candela per square metre is sometimes called the nit. Illuminance: E v: lux (= lumen per square metre) lx (= lm/m 2) L −2 ⋅J: Luminous flux incident on a surface Luminous exitance, luminous emittance M v: lumen per square metre lm/m ...
For each photometric system a set of primary standard stars is provided. A commonly adopted standardized photometric system is the Johnson-Morgan or UBV photometric system (1953). At present, there are more than 200 photometric systems. [citation needed] Photometric systems are usually characterized according to the widths of their passbands:
Radiosity of a surface, denoted J e ("e" for "energetic", to avoid confusion with photometric quantities), is defined as [3] = =, +, +,, where ∂ is the partial derivative symbol; is the radiant flux leaving (emitted, reflected and transmitted)
Comparison of photometric and radiometric quantities 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.
The operating principles are the same but the results are given in units such as photons/cm 2 or photons·cm −2 ·sr −1 rather than W/cm 2 or W·cm −2 ·sr −1. Due to their individual photon counting nature, these instruments are limited to observations where the irradiance is low.