the process by which the eye changes focus from one distance to another

the process by which the visual system becomes accustomed to more or less light or light of a different colour than it was exposed to during and immediately preceding period. It results in a change in the sensitivity of the eye to light. See scotopic vision, photopic vision, chromatic adaptation. Note: adaptation is also used to refer to the final state of the process, as reaching a condition of dark adaptation or light adaptation.

lighting throughout an area that produces general illumination

unit of wavelength equal to 10-10m (one ten-billionth of a metre).

a lambertian unit of luminance equal to 1/π cd/m². This unit is now deprecated.

a current limiting device used with discharge lamps.

the angle between the two directions for which the intensity is 50% of the maximum.

attribute of visual sensation according to which an area appears to emit more or less light.

the SI unit of luminous intensity.

measure of the degree of colour shift objects undergo when illuminated by a light source compared with the colour of those same objects when illuminated by a reference source of comparable colour temperature.

the absolute temperature of a black body whose chromaticity most nearly resembles that of the light source.

light received directly or indirectly from the sun.

device used to redirect or scatter the light from a source.

quotient of the luminous flux emitted by a source divided by the power consumed by that source.

lighting provided for use when the supply to the normal lighting fails.

see luminous flux.

imperial unit of illuminance.

condition of vision in which there is discomfort or reduction in the ability to see details caused by unsuitable distribution or range of luminance.

density of luminous flux incident on a surface.

see luminous intensity.

source of optical radiation, usually visible.

light emitting diode.

SI unit of luminous flux.

apparatus which distributes, filters or transforms the light transmitted from one or more lamps.

photometric measure of luminous intensity per unit area projected in a given direction.

measurement of quantities associated with light.

device used to redirect light from a source by reflection.

numerical value describing discomfort glare in an interior environment.

SI unit of power.