Not all area light are created equal. Even if you’ve done all the research for choosing the perfect color temperature, Lumen output, and HID wattage, choosing the wrong light distribution type could have a major negative impact on your lighting design.
The light distribution type of a fixture represents the pattern of light emitted by the fixture. Some distribution types are better suited for certain areas than others. Whether in an indoor warehouse or an outdoor parking lot, there’s a preferred light distribution for you.
Type I light distribution has a long, narrow light pattern that is best suited for sidewalks, walkways, and aisle ways. Fixtures with this type of light distribution are typically installed near the center of the pathway. The two-way lateral pattern emits light on two sides of the fixture opposite each other with little to no light spilling out the other two sides. The type I light distribution is often used to light the aisles of retail spaces or warehouses with tall shelving. Placing these fixtures parallel to aisles is about 50 percent more efficient than a perpendicular alignment, meaning more of the light shines where you need it and doesn’t get lost above the shelves.
Type II light distribution is the narrowest distribution you can find that still emits some light forward. Fixtures with this light pattern are most often installed on the edges of smaller side streets, jogging paths, and wide walkways. This light distribution type illuminates pathways about 1.5 times wider than the mounting height of the fixture. Meaning if the fixture is mounted 10 feet high, the light will be cast about 15 feet wide.
Very similar to but wider than a type II light distribution, type III distributions cast a light pattern that is 2.75 times wider than the fixture’s mounting height. Therefore, our 10 foot tall example fixture will cast a light about 27.5 feet in width. This light pattern is intended for perimeter lighting of parking lots and along the edges of an open area as well as large roadways and parking lot aisles. It casts more light forward so that it can be used to light roads and pathways from the side of the road rather than being installed in the median. Fixtures with a type III light distributions are a popular choice for larger roadways and parking lot aisles.
Type IV light distribution has the widest forward throw light pattern, meaning much of the light is pushed outward with very little light spilling behind the fixture. This light distribution type is a lot more rounded than the first three types discussed here. Fixtures with this distribution type are usually installed along perimeters and the sides of building for security lighting. They are also a good choice for recreational outdoor sports lighting.
Designed for large open spaces like intersections, large parking lots, and roadway medians, type V light distributions direct light in a circular or square pattern in all directions around the fixture. This light distribution type is best suited for large open spaces like roadway medians and intersections, large parking lots, and anywhere an evenly spread pattern of light is required. The main difference between a regular type V distribution and a type V square distribution (sometimes denoted as “type VS”) is that the square light patterns are better in areas that need a more defined edge for the intended illuminated area.
Understanding LED Distribution Types
With LED technology it is now easier than ever to predict and direct where the light will go.
This is only for a quick reference on what each Distribution Pattern will generally look like. Actual luminaire distribution pattern depend on the applications and the environment.
The type I distribution is great for lighting walkways, paths and sidewalks. This type of lighting is meant to be placed near the center of the pathway. This provides adequate lighting for smaller pathways.
Type I is a two-way lateral distribution having a preferred lateral width of 15 degrees in the cone of maximum candlepower. The two principal light concentrations are in opposite directions along a roadway. This type is generally applicable to a luminaire location near the center of a roadway where the mounting height is approximately equal to the roadway width.
The type II distribution is used for wide walkways, on ramps and entrance roadways, as well as other long, narrow lighting. This type is meant for lighting larger areas and usually is located near the roadside. You’ll find this type of lighting mostly on smaller side streets or jogging paths.
Type II light distributions have a preferred lateral width of 25 degrees. They are generally applicable to luminaires located at or near the side of relatively narrow roadways, where the width of the roadway does not exceed 1.75 times the designed mounting height.
The type III distribution is meant for roadway lighting, general parking areas and other areas where a larger area of lighting is required. Type III lighting needs to be placed to the side of the area, allowing the light to project outward and fill the area. This produces a filling light flow.
Type III light distributions have a preferred lateral width of 40 degrees. This distribution is intended for luminaires mounted at or near the side of medium width roadways or areas, where the width of the roadway or area does not exceed 2.75 times the mounting height.
The type IV distribution produces a semicircular light meant for mounting on the sides of buildings and walls. It’s best for illuminating the perimeter of parking areas and businesses. The intensity of the Type IV lighting has the same intensity at angles from 90 degrees to 270 degrees.
Type IV light distributions have a preferred lateral width of 60 degrees. This distribution is intended for side-of-road mounting and is generally used on wide roadways where the roadway width does not exceed 3.7 times the mounting height.
Type V produces a circular distribution that has the same intensity at all angles. This distribution has a circular symmetry of candlepower that is essentially the same at all lateral angles. It is intended for luminaire mounting at or near center of roadways, center islands of parkway, and intersections. It is also meant for large, commercial parking lot lighting as well as areas where sufficient, evenly distributed light is necessary
Type VS produces a square distribution that has the same intensity at all angles. Type 5S (square) LED Distribution pattern. This distribution has a square symmetry of candlepower that is essentially the same at all lateral angles. It is intended for luminaire mounting at or near center of roadways, center islands of parkway, and intersections.
It is also meant for large, commercial parking lot lighting as well as areas where sufficient, evenly distributed light is necessary. Type VS is used where the light pattern needs a more defined edge.