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

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).

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.

illuminance

[ə′lü·mə·nəns]
(optics)
The density of the luminous flux on a surface. Also known as illumination; luminous flux density.

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.
References in periodicals archive ?
Office cubicles were lighted with either a dimmable ceiling mounted T5 luminaire or with a switchable desktop CFL luminaire, that had multiple switching levels for different illuminances, and a T5 ceiling luminaire that provided ambient light at constant level.
The result of simulation focused on the illuminance work plane for C2GL office building.
This example assumes a desired Minimum Initial Illuminance of 2.
The illuminance recommendation for Category P is 300 lux, or 30 footcandles for the 25-65 age column in the Illuminance Determination System of the IES Handbook, 10th Edition.
Figure 2 proves that illuminances calculated on a task surface 1 m below the light source (Fig.
Daylight autonomy defines the time fraction when the work plane illuminance set point met by daylight alone, so it is more reasonable to use method (ii) to evaluate the overall space daylight performance from the simultaneous illuminances of many evaluated points in the space.
Experiment 1 used three types of lamp, two illuminances and three levels of interior colorfulness, giving 18 stimulus combinations.
This difference occurred primarily because (1) the 16 sensors probably were not enough to represent the average illuminance and (2) the outdoor illuminance measurements, which were measured by the weather station system and used in the simulation, were not completely synchronized with the measurements of the indoor illuminances.
The current indoor lighting recommendations give ranges of illuminance values for different types of rooms and activities [10].
Her concern was with the inadequacy of current lighting standards based on roadway illuminance for ensuring the visibility of targets for drivers and for making the sidewalks appear safe to pedestrians.