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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}


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}


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.


[[Category:Visual perception
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