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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 imaging[]

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 luminosity[]

The following relations hold

(if the target is perfectly opaque)


is the Luminosity.
is the number of interactions.
is the number density of a particle beam, e.g. within a bunch.
is the total cross section.
is the differential solid angle.
is the differential cross section.

For an intersecting storage ring collider:


is the revolution frequency
is the number of bunches in one beam in the storage ring.
is the number of particles in each beam
is the cross section of the beam.


[[Category:Visual perception

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