illuminance

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illuminance:

see photometryphotometry
, branch of physics dealing with the measurement of the intensity of a source of light, such as an electric lamp, and with the intensity of light such a source may cast on a surface area.
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Illuminance

A term expressing the density of luminous flux incident on a surface. This word has been proposed by the Colorimetry Committee of the Optical Society of America to replace the term illumination. The definitions are the same. The symbol of illumination is E, and the equation is E = dF/dA, where A is the area of the illuminated surface and F is the luminous flux. See Luminous flux, Photometry

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

Illuminance

Commonly called light level, illuminance refers to the light intensity arriving on a surface, measured in foot-candles (fc). It is the standard international unit that is used to measure the amount of light per unit of surface area, also known as lux (lx). Measurements of illuminance are used to select lighting fixtures and to evaluate a lighting design. The photometric data to be considered include the luminous-intensity distribution curve (LIDC), the coefficient of utilization (CU), and the light loss factor (LLF).
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 It might be outdated or ideologically biased.

Illuminance

(at a point of a surface), a unit of light, equal to the ratio of the luminous flux incident upon a small surface element ΔS containing the point being considered to the area of ΔS. Stated differently, illuminance is the surface density of the luminous flux. If the dimensions of the source of light are small in comparison with the distance l of the source from ΔS, then the illuminance E = I cos α/l2, where I is the luminous intensity of the source and α is the angle of incidence of the light upon ΔS, that is, the angle between the direction of the luminous flux and a line perpendicular to ΔS. Units of illuminance are the lux and the phot: 1 phot = 104 lux.

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

illuminance

[ə′lü·mə·nəns]
(optics)
The density of the luminous flux on a surface. Also known as illumination; luminous flux density.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

illuminance

The density of luminous power, also called illumination. One lumen of luminous flux, uniformly incident on 1 square foot of area, produces an illuminance of 1 footcandle; in SI units, one lumen of luminous flux, uniformly incident on 1 square meter of area, produces an illuminance of 1 lux.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
References in periodicals archive ?
The result of simulation focused on the illuminance work plane for C2GL office building.
This example assumes a desired Minimum Initial Illuminance of 2.0fc, using luminaires mounted on 14' poles.
However, applying (1) to these far-field measurements leads to erroneous predictions of the illuminances. Figure 2 proves that illuminances calculated on a task surface 1 m below the light source (Fig.
The daylighting model consists of the calculation of incident and transmitted illuminance using the Perez model (Perez et al., 1990), and calculation of work plane illuminance using the radiosity method.
Four color palettes (yellow, green, blue and red) were observed under two different types of lamp and two different illuminances and these were ranked in order according to six bipolar semantic differential scales including bright-dim and clear-hazy, essentially a four-alternative forced-choice task.
Lighting standards and codes usually provide recommended illuminance ratios between the task area and its surroundings according EN 12 464-1 [21].
In the balanced stimulus frequency null-condition trials, the same three reference illuminances were used (2.0 lx, 7.5 lx and 15.0 lx) but the comparison booth was presented at only three levels, these being equal illuminance to, and one S-class step above and below, the reference illuminance (this required extrapolation of the S-series to create further classes of illuminance at each end of the series).
2) By a certain angle [phi] between the normal and the beam of the light then the illuminance depends on the angle of the light and distance r between the light source and the illuminated surface
Another limitation is that, since illuminance from direct sun is not considered in the calculation of daylight factor, it's in variant to building orientation or location.
This paper analyzes empirical constraints from the shape of the contrast sensitivity function (CSF) at several illuminance levels and from the relationship between illuminance and visual acuity, showing that the DeVries-Rose to Weber transition with sine-wave gratings can only hold at very low spatial frequencies.
It should be emphasized that the lighting rig simulates the glare illuminance on the driver's eye of a continuous stream of oncoming cars.

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