LOR
Acronym for Light Output Ratio. It is a percentage value obtained by the ratio
between the luminous flux of a device and the luminous flux installed.
Louvre screen
Screen whose shielding elements are lamellae made of opaque or translucent material.
Lumen
SI unit of luminous flux. The lumen (lm) is the luminous flux emitted in a unit solid
angle by a uniform point source having a luminous intensity of 1 candela.
Luminance
Photometric valuee showing the luminous power of a light source for solid angle unit
and for surface unit. It is used to define how bright a surface is at a certain angle.
In the International System it is measured in candles per square metre (cd/m2), in the
United States in foot-lambert.
Luminous flux
Photometric value showing the amount of light emitted by a light source. It comes
from the radiant flux (W) and is expressed in lumen.
Luminous intensity
Photometric value expressing the lighting power of a source for solid angle unit. It is
an essential value in the International System; it is used to define how bright a specific
point is at a certain angle. It is measured in candles (cd).
Lux (lx)
SI unit of illuminance. Illumination produced on a surface with an area of 1 square
metre by a luminous flux of 1 lumen uniformly distributed on this surface.
M
MacAdam Ellipse
In CIE chromatic diagrams, these are elliptical areas defining the ability of the human
eye in perceiving colour differences from the centre of the elliptical area. E.g., a Step3
MacAdam Ellipse means that on average the human eye is able to perceive 3 different
colours from the centre to the border of the ellipse.
Mesopic vision
Intermediate vision between photopic and scotopic vision.
Minimum/average illuminante
See definition of ‘uniformity’.
