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Lighting Distribution Patterns Outdoor Lighting

Time:2014-11-16 Hits:1207 Compile:bbtlight

When specifying lighting fixtures for outdoor applications is it often useful to know the type of lighting distribution a specific fixture has, most of the time the type of distribution is governed by the application it is used for. But how exactly is a distribution defined? The IESNA (IIlluminating Engineering Society of North America) defines lighting distribution based on the horizontal pattern or lateral distribution and the amount of light at different vertical angles.

The distribution names are represented by roman numerals : Type I, Type II, Type III, Type IV & Type V. So when lighting manufacturers say type II or IV this is what they are refering to. So lets take a look at each distribution:


Type I:

This distribution is ideal for lighting sidewalks and narrow walkways, usually placed at the centre of the pathway and provides a lighting distribution that is symmetrical. The width of the light thrown is approximately equal to the the mounting height of the fixture. 


Type II:

 Type II has a distribution suited for wider paths (side streets and jogging paths) and driveways, usually placed on the edge of the area. It lights up an area 1.5 times wider than the mounting height of the fixture.


Type III:
This type of distribution is meant for roadways, general parking, lawns and other areas where large quantity of lighting is needed. Also placed at the edge of the area and light is projected on to the area.  It lights up an area approximately 2.75 timeswider than the mounting height.


Type IV:

 Works well for lighting fixtures mounted on walls, best for illuminating the perimeter of parking areas and buildings. Also known as Forward Throw or Asymmetric. It lights up an area approximately 2.75 times wider than the mounting height.


Type V:

This distribution is meant for large commercial parking areas or any area whereevenly distributed light is required. Type V has a characteristic square or circular distribution with equal intensity at all angles.