IESNA and NEMA Light Distribution Types
Before selecting an area lighting fixture, it is important to consider its light distribution pattern. The Illuminating Engineering Society of North America (IESNA) and the National Electrical Manufacturers Association (NEMA) have established classifications for light distribution patterns to help consumers choose the right fixtures for their applications.
IESNA Light Distribution Patterns
The Illuminating Engineering Society of North America is an organization dedicated to improving lighting quality through education, research, and development of lighting standards. IESNA developed a classification system of light distribution patterns based on how light is distributed in a horizontal plane. These lighting distribution types measure the point where half of the luminous intensity, or the measure of a wavelength in a particular direction, reaches. IESNA distribution types provide guidance for the design and installation of various outdoor lighting systems, such as parking lots, roadways, and walkways.
Type I
The Type I distribution pattern lights long, narrow areas such as pathways, walkways, or sidewalks from a central position and produces a skinny, rectangular oval pattern. Type I lights follow a two-way lateral distribution where the light source is directed outward in opposite directions. The mounting height for a Type I light should be approximately equal to the area width.
Type II
A Type II light distribution is used to light wide walkways, sidewalks, and bike paths from the side. These lights direct light outwards to the sides similar to Type I, but also distribute light forward. The area width for Type II should be no more than 1.75 times the mounting height.
Our 90W LED Street/Roadway Light follows a Type II distribution pattern and is ideal for pathways and residential roads.
Type III
The Type III light distribution illuminates areas such as roadways, parking lots, or intersections from the edge. It distributes light forward farther than Type II and is therefore used to light wider pathways and roadways. For installation, the area width should be no more than 2.75 times the mounting height.
Our 300W LED Flood Light with Yoke Mount has a Type III distribution pattern and is used for lighting parking lots, roadways, and parks.
Type IV
A Type IV light distribution pattern is designed to provide high illumination over large areas such as highways, parking lots, or airport runways. This pattern mostly throws light forward instead of sideways. The area width for a Type IV light should be no more than 3.75 times the mounting height.
Type V
Type V directs light outwards in a circular, symmetrical pattern. Use Type V lights for large open areas such as parking lots, sports fields, and intersections. Type V ensures equal light distribution at all positions with a 360-degree circular distribution.
Our 200W LED High Power Area Flood Light has a Type V distribution pattern and is best suited for parking lots and stadiums.
IESNA Light Distribution Range
The IESNA distribution range shows the location of the light’s maximum intensity point. Calculate each distribution range using the equations below:
- VS Distribution Range= <1✕H
- S Distribution Range= 1✕H to 2.25✕H
- M Distribution Range= 2.25✕H to 3.75✕H
- L Distribution Range= 3.75✕H to 6✕H
- VL Distribution Range= >6✕H
Both the light distribution type and range are used to classify lights. For example, an ‘III-M’ light has a distribution type ‘III’ and a distribution range ‘M’. The default distribution range is “M” for most area lights.
Shop our outdoor commercial lights using IESNA distribution types.
NEMA Light Beam Types
The National Electrical Manufacturers Association is a trade association representing manufacturers of electrical and medical technologies in the United States. NEMA has developed a classification system for light distribution patterns that are classified based on the way light is distributed in a vertical and horizontal plane. This classification measures 10% of the maximum horizontal and vertical beam intensity area. Typically the wider the beam spread is, the shorter the projection distance will be if the wattage is the same. NEMA beam spread types are mainly used to categorize floodlights and spotlights.
Lights with different horizontal and vertical NEMA types are represented by two numbers: Horizontal Type # X Vertical Type #. For example, a light with a Type 7 horizontal width and a Type 6 vertical height would be considered NEMA 7 X 6. Our 70W LED Flood Light with Selectable Color Temperature has a NEMA 7 X 6 beam type and is ideal for building facades and security lighting.
Shop our various residential landscape spot lights, residential landscape flood lights, and commercial flood lights by NEMA beam spread type.
by Elizabeth Schlaker
Lead SEO Specialist
Elizabeth loves writing about all the creative ways you can use strip lights and landscape lights. In her free time, you can catch her trying out new DIY projects, reading books, and traveling.
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