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Cognitive Psychology: Attention · Learning · Memory · Motivation · Perception · Thinking

In psychophysics luminosity is the perceived brightness of an object as opposed to its objectively measured physical luminance, although of course these are usually related.

In photometry and color imagingEdit

In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.

Main article: HSL color space

The "L" in HSL color space is sometimes said to stand for luminosity. "L" in this case is calculated as 1/2 (MAX + MIN), where MAX and MIN refer to the highest and lowest of the R'G'B' components to be converted into HSL color space.

Elementary relations for luminosityEdit

The following relations hold

$L = \rho v \,$ (if the target is perfectly opaque)

$\frac{dN}{dt} = L \sigma$

$\frac{d\sigma}{d\Omega} = \frac{1}{L} \frac{d^{2}N}{d\Omega dt}$

where

$L$ is the Luminosity.

$N$ is the number of interactions.

$\rho$ is the number density of a particle beam, e.g. within a bunch.

$\sigma$ is the total cross section.

$d\Omega$ is the differential solid angle.

$\frac{d\sigma}{d\Omega}$ is the differential cross section.

For an intersecting storage ring collider:

$L = f n \frac{N_{1} N_{2}}{A}$

where

$f$ is the revolution frequency

$n$ is the number of bunches in one beam in the storage ring.

$N_{i}$ is the number of particles in each beam

$A$ is the cross section of the beam.

ReferencesEdit

[[Category:Visual perception

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 {{ExpPsy}}
-{{PsyPerspective
 In [[psychophysics]] '''luminosity''' is the perceived brightness of an object as opposed to its objectively measured physical [[luminance]], although of course these are usually related.
 ==In photometry and color imaging==
-{{main|luminance}}
-In [[photometry]], ''luminosity'' is sometimes incorrectly used to refer to [[luminance]], which is the density of [[luminous intensity]] in a given direction. The [[SI]] unit for luminance is [[candela]] per [[square metre]].
-{{main|luma (video)}}
+In [[photometry]], ''luminosity'' is sometimes incorrectly used to refer to [[luminance]], which is the density of [[luminous intensity]] in a given direction. The [[SI]] unit for luminance is [[candela]] per [[square metre]].
 {{main|HSL color space}}

Wikia

Changes: Luminosity

Latest revision as of 10:29, July 8, 2007

In photometry and color imagingEdit

Elementary relations for luminosityEdit

ReferencesEdit