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The luminous intensity of any surface in a given direction per unit of projected area of the surface viewed from that direction. The International Commission on Illumination defines it as the quotient of the luminous intensity in the given direction of an infinitesimal element of the surface containing the point under consideration, by the orthogonally projected area of the element on a plane perpendicular to the given direction. Simply, it is the luminous intensity per unit area. Luminance is also called photometric brightness.

Since the candela is the unit of luminous intensity, the luminance, or photometric brightness, of a surface may be expressed in candelas/cm2, candelas/in.2, and so forth.

The stilb is a unit of luminance (photometric brightness) equal to 1 candela/cm2. It is often used in Europe, but the practice in America is to use the term candela/cm2 in its place.

The apostilb is another unit of luminance sometimes used in Europe. It is equal to the luminance of a perfectly diffusing surface emitting or diffusing light at the rate of 1 lumen/m2. See Luminous intensity, Photometry

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.


The physical measure of brightness, or luminous intensity per unit of projected area of any surface, as measured from a specific direction. It is the amount of visible light. leaving a point on a surface in a given direction. This “surface” can be a physical surface or an imaginary plane, and the light leaving the surface can be due to reflection, transmission, and/or emission. The standard unit of luminance is candela per square meter (cd/m2).
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(L), a photometric quantity equal to the ratio of luminous flux d2ф and geometric factor dΩdA cos θ:

L = d2ф/dΩdA cos θ

where dΩ is the solid angle filled with radiation, dA is the area of the emitting or illuminated surface, and θ is the angle between the normal to the surface and the direction of the radiation.

Two special definitions of great practical interest follow from the general definition of luminance. First, luminance may be defined as the ratio of the luminous intensity I of a surface element and the area of the element’s projection perpendicular to a given direction: L = dI/dA cos θ. Second, luminance may be defined as the ratio of the illuminance E at a point of a plane that is perpendicular to the direction to the source and the unit solid angle occupied by the flux produced by the illuminance:

L = dE/dΩ cos θ.

Luminance is measured in candelas per m2. It is the photometric quantity that is most directly associated with visual sensations, because the illuminance of the image of an object on the retina is proportional to the luminance of the object.

In the system of radiometric quantities, the quantity that is analogous to luminance is called radiance. Radiance is measured in watts per steradian per m2.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


The ratio of the luminous intensity in a given direction of an infinitesimal element of a surface containing the point under consideration, to the orthogonally projected area of the element on a plane perpendicular to the given direction. Formerly known as brightness.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


The luminous intensity of any surface in a given direction per unit of projected area of the surface, as viewed from that direction; a directional property of luminous radiation.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.


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The amount of brightness, measured in lumens, that is given off by a pixel or area on a screen. For example, dark red and bright red would have the same chrominance, but a different luminance. Bright red and bright green could have the same luminance, but would always have a different chrominance. See luma.
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The order of stimuli for each participant was as follows: In the first part of the experiment (which was always the detection distance task) 30 trials were presented in two blocks, each of which consisted of all 15 combinations of luminance and color.
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Figure 13 shows the measurement results of the spatial luminance emitted from the injection-molded LGPs having convex and concave MLAs at the nine different locations indicated in Fig.
The anchoring theory can explain the lightness compression effect found by Cataliotti and Gilchrist (1995; see also Gilchrist & Cataliotti, 1994) when presenting a luminance staircase in the context of experimental settings similar to the ones used in the famous Gelb demonstration (Gelb, 1929/1938; hereafter the "Gelb effect").
Luminance is a photometric measure which represents the intensity of the light emitted, reflected or passing through objects in a scene and it is basically an indicator of how bright an object in that scene is.
The imaging luminance meter (ILM) is based on a calibrated and optimised digital camera, equipped with an optical system that includes a V-Lambda correction filter and photo sensitive CMOS image sensor.
While luminance range masking limits the editing effects to a range of brightness or luminance,color range masking uses a color value or a range of color values to make an accurate mask.