LIGHTING GLOSSARY
Proximal colour temperature
Tones of light that correspond to the temperature of a normalised body (Plank radiator).
UNIT: K (Kelvin degrees)
UNIT: K (Kelvin degrees)
Punctiform source
A source of radiation of negligible dimensions with respect to the distance between the source and the irradiated surface.
Luminance source
The lowest luminance level that can provoke a perceivable stimulus.
Appliance performance
The ratio between the lighted flow issued by the appliance and the sum of the issued flows.
The UNI 10380 standard deals with the specifications for interior artificial lighting in details.
The UNI 10380 standard deals with the specifications for interior artificial lighting in details.
Useful plane
Reference surface defined as the plane where the visual task is usually carried out.
Luminance
Ratio between the light intensity "L" issued, reflected or transmitted from the surface S in the assigned direction and the apparent area of the same surface.
UNIT: cd/m2
L = I / S cos a
UNIT: cd/m2
L = I / S cos a
Light intensity
A light source irradiates its light flow in different directions and with variable intensity. The light intensity corresponds to the intensity of light irradiated in a given direction.
UNIT: cd (candle)
UNIT: cd (candle)
Chromatic yield indicator
Quantity assessment of the level of agreement between the psychophysical colour of an item illuminated by the test light and that of the same item illuminated by a reference light.
Illumination
At a point on a surface, it is the ratio between a light flow received from a surface and the area of the same surface that is perpendicular to the flow direction.
UNIT: lx (lux)
The illumination produced from a light flow of 1 lm which falls evenly onto a surface of 1m2 is 1 lx
UNIT: lx (lux)
The illumination produced from a light flow of 1 lm which falls evenly onto a surface of 1m2 is 1 lx
Flux
Amount of light given into space by a source.
UNIT: lm (lumen)
UNIT: lm (lumen)
Use factor
Ratio between the light flow received from the reference surface and the sum of the individual flows from the installed lamps.
Reflection factor
Ratio between the reflected light flow and the incident flow at the given conditions.
Maintenance factor
Ratio between average illumination on the worktop after a certain time using the installation and the average illumination given in the same conditions with a new installation.
Luminous Efficiency
The ratio between the light flow issued by the lamp and the absorbed electric power. It gives the economic level with which the electric power absorbed is transformed into light.
UNIT: lm/W
UNIT: lm/W
Luminance contrast
Relative difference in luminance between two parts of a visual
(L object - L background) / L background
(L object - L background) / L background
Solid angle
Angular opening subtended to the centre of a spherical cap of an area that is numerically the same as the square of the radius sr (steradian).
Glare
Condition of discomfort or reduced visual capacity caused by unsuitable distribution or luminance gradient or excessive contrast in space or time.