Luminous intensity curves of LED illuminators

Standard diagrams of angular distribution of luminous intensity a.k.a. luminous intensity curves (LIC) can be found in the GOST 17677-82 (ГОСТ 17677-82) standard.

They are classified according to two independent indicators: the direction of maximum luminous intensity and the LIC aspect ratio which is understood as the ratio of maximum luminous intensity in the given meridional plane to the arithmetic mean luminous intensity of the illuminating device for the said plane.

A luminous intensity curve is a diagram showing dependence of the luminous intensity of the illuminating device upon meridional and equatorial angles obtained through its cross-section by a plane or a surface.

LICs are subdivided into seven types, the table below showing their main characteristics

Designation (Name)
Symbol used
Aspect ratioFocus area of maximum luminous intensityLight intensity curve
ConcentratedK≥30-15° К
DeepD2-30-30ºГ
CosineC1,3-20-35ºД
Semi-ExpandedS1,335-55º Л
ExpandedE1,355-85ºШ
UniformU1,30-180ºМ
SineS1,370-90ºС

Luminous intensity curves of illuminators

  • For highways, streets, motorway tunnels, pedestrian overpasses and underpasses, housing and utility infrastructure, public buildings, illuminators are used that have LIC type SE and E in one of the planes and K or D in another one.
  • Fr industrial indoor areas, LIC type K, D, C direct light illuminators are recommended.
  • For ambient lighting of offices, LIC type D and C direct and dissipated light illuminators are applied.
  • For highlighting of special, reserved areas, interior architectural solutions and interior details, LIC type K illumination devices are the best option.
  • For arrangement of reflected or dimmed light (for example, in the lobby of a building), the LIC type S reflected light illuminators are predominantly used.

For illumination of indoor hallways of residential tower blocks and other buildings, utility rooms, accommodation spaces, LIC type U illuminators are used.