Ever noticed dark spots in your outdoor space? Poor light distribution doesn’t just affect visibility—it can compromise safety and efficiency too. The right LED light distribution ensures even illumination, eliminating shadows and enhancing both functionality and aesthetics. Let’s explore how to make the best choice for your outdoor lighting needs.

Getting the right LED light distribution is key to effective outdoor lighting. It determines how light spreads across an area, directly impacting visibility, safety, and energy efficiency. The Illuminating Engineering Society (IESNA) has categorized light distribution into different types—Type I, II, III, IV, and V—each designed for specific applications. By understanding IESNA classifications, BUG ratings, and NEMA classifications, you can optimize lighting for streets, sports fields, parking lots, and more.

Now, let’s break down the fundamentals of light distribution and why it matters.

What is Light Distribution?

Light distribution refers to how a luminaire projects light over an area. It defines the shape and intensity of illumination, ensuring proper coverage and reducing energy waste. Some distributions are narrow and focused, perfect for pathways, while others are broad, ideal for large spaces like parking lots.

Choosing the right distribution ensures safety, functionality, and visual appeal—key factors in any outdoor lighting setup.

IESNA Light Distribution Types

The Illuminating Engineering Society (IES) classifies light distribution based on how luminaires project light across a specific area. This system helps in selecting the best lighting solution for any given space. One important factor in these classifications is Mounting Height (MH), which affects the spread and reach of light.

Lateral Light Distribution

Lateral light distribution determines how light spreads horizontally. It is categorized into different “types,” depending on the width of the light spread.

Type I

• Pattern: Narrow, symmetric.
• Coverage: Light extends 1 MH on both sides of the luminaire.
• Best for: Walkways, pathways, roadways, and high-mast lighting.

Type II

• Pattern: Narrow, asymmetric.
• Coverage: Extends between 1 MH and 1.75 MH on the street side.
• Best for: Roadways, bike paths, and walkways needing slightly wider coverage.

Type III

• Pattern: Wide, asymmetric.
• Coverage: Spreads 1.75 MH to 2.75 MH on the street side.
• Best for: Roadways, parking lots, and area lighting requiring broader coverage.

Type IV

• Pattern: Asymmetric forward throw.
• Coverage: Extends beyond 2.75 MH but less than 3.7 MH on the street side.
• Best for: Perimeter lighting on poles or walls.

Type V

• Pattern: Symmetric, circular.
• Coverage: Evenly spreads light in all directions.
• Best for: Parking lots and open areas requiring uniform illumination.

Type VS

• Pattern: Symmetric, square.
• Coverage: Provides a square-shaped distribution with consistent intensity.
• Best for: Parking lots and large spaces where even light coverage is needed.

Vertical Light Distribution

Along with lateral spread, luminaires also have different vertical distributions, categorized based on how far the light reaches from its mounting height.

• Very Short: Max intensity occurs between 0 – 1.0 MH.
• Short: Max intensity falls between 1.0 – 2.25 MH.
• Medium: Max intensity is centered between 2.25 – 3.75 MH.
• Long: Max intensity extends between 3.75 – 6.0 MH.
• Very Long: Max intensity reaches beyond 6.0 MH.

Understanding both lateral and vertical light distributions ensures that your lighting setup is efficient, effective, and tailored to your needs.

What is a BUG Rating?

The BUG rating¹ system (Backlight, Uplight, and Glare) helps assess how a luminaire performs and its impact on the environment.

• Backlight (B): Measures how much light spills behind the fixture.
• Uplight (U): Determines upward light emissions, which contribute to light pollution.
• Glare (G): Indicates the amount of direct light that can cause visual discomfort.

A lower BUG rating means better light control, reduced pollution, and improved efficiency—critical for outdoor applications.

Cutoff Classifications

Though largely replaced by the Luminaire Classification System (LCS), traditional cutoff classifications are still referenced in many IESNA documents. These include:

Full Cutoff

• Definition: No light is emitted above 90 degrees from the nadir (horizontal).
• Best for: Areas needing strict light control, preventing light spill and glare.

Cutoff

• Definition:
• No more than 2.5% of light is emitted at or above 90 degrees.
• No more than 10% of light is emitted at an 80-degree vertical angle.
• Notes: Offers good control while allowing some upward light.

Semi-Cutoff

• Definition:
• No more than 5% of light is emitted at or above 90 degrees.
• No more than 20% of light is emitted at an 80-degree vertical angle.
• Notes: Suitable for applications where some uplight is acceptable.

Non-Cutoff

• Definition: No restrictions on light distribution—light is emitted freely in all directions.
• Best for: Decorative lighting where wider coverage is needed.

While the LCS system is now more commonly used, understanding these classifications is still important for legacy projects and specific lighting applications. Each classification serves a purpose in controlling light spill, reducing glare, and ensuring compliance with lighting standards.

By understanding light distribution, BUG ratings, and cutoff classifications, you can ensure your outdoor lighting system delivers the right balance of brightness, efficiency, and safety. Choosing the right luminaire not only enhances visibility but also improves energy use and minimizes unnecessary light pollution.

NEMA Light Distribution for Sports and Flood Lighting

The National Electrical Manufacturers Association (NEMA) classifies light distribution patterns based on beam angles, primarily for sports and floodlighting applications. These classifications help determine the best luminaire for achieving the right coverage and performance. NEMA categorizes beam spreads into seven types, each suited for different lighting needs.

NEMA Type 1 (Very Narrow)

• Beam Angle: Less than 10 degrees.
• Applications: Used for spotlighting, highlighting tall structures, or illuminating long distances, such as high towers or architectural features.

NEMA Type 2 (Narrow)

• Beam Angle: 10 to 18 degrees.
• Applications: Ideal for precision lighting, such as small sports courts or focused floodlighting in specific zones.

NEMA Type 3 (Medium Narrow)

• Beam Angle: 18 to 29 degrees.
• Applications: Commonly found in smaller sports fields or localized floodlighting setups.

NEMA Type 4 (Medium)

• Beam Angle: 29 to 46 degrees.
• Applications: A versatile option for mid-sized sports fields, parking lots, and general floodlighting.

NEMA Type 5 (Medium Wide)

• Beam Angle: 46 to 70 degrees.
• Applications: Suitable for larger areas requiring broader illumination, such as recreational sports fields or parking lots.

NEMA Type 6 (Wide)

• Beam Angle: 70 to 100 degrees.
• Applications: Used in large sports fields, stadiums, and other open areas needing even light distribution.

NEMA Type 7 (Very Wide)

• Beam Angle: Greater than 100 degrees.
• Applications: Best for lighting wide areas like public parks or industrial zones where uniform brightness across a large space is critical.

What Type of Lighting is Used in Outdoor Areas?

Outdoor lighting enhances safety, functionality, and aesthetics across various spaces. The right type of lighting depends on the location, whether it’s for streets, parking lots, sports fields, or building exteriors. Here are some of the most common outdoor lighting solutions:

1. LED Street Lights

• Description: Designed to provide even, energy-efficient lighting for roadways and sidewalks.
• Applications: Streets, highways, and pedestrian pathways.
• Features: Long lifespan, reduced glare, and directional lighting to minimize light pollution.

2. Flood Lights

• Description: High-intensity lights designed to cover large areas.
• Applications: Stadiums, sports fields, industrial sites, and parking lots.
• Features: Adjustable beam angles, high lumen output, and durability in outdoor environments.

3. Wall-Mounted Fixtures

• Description: Installed on building exteriors to provide perimeter lighting and accentuate architecture.
• Applications: Commercial buildings, residential complexes, and public areas.
• Features: Weather-resistant design, motion sensor options for security.

4. Bollard Lights

• Description: Short, ground-mounted fixtures used for pathway lighting.
• Applications: Gardens, parks, and walkways.
• Features: Decorative designs, energy-efficient operation, and soft ambient lighting.

5. High Mast Lights

• Description: Tall lighting structures with multiple luminaires for widespread coverage.
• Applications: Highways, stadiums, and airports.
• Features: High brightness, minimal maintenance, and large coverage area.

6. Area Lights

• Description: Provide uniform illumination over large open spaces.
• Applications: Parking lots, public parks, and commercial outdoor spaces.
• Features: High lumen output, durable construction, and energy efficiency.

Choosing the right outdoor lighting depends on the space’s specific needs, whether it’s visibility, security, or aesthetic appeal. LEDs remain the preferred option due to their energy efficiency, long lifespan, and adaptability.

Lighting Distribution Applied in Outdoor Luminaires

Proper lighting distribution² ensures the best performance, energy efficiency, and safety for outdoor luminaires. Different outdoor applications require specific light distribution types to match their purpose.

Street and Roadway Lighting

• Description: Provides uniform lighting along roadways and pedestrian paths.
• Preferred Distribution Types:
• Type II: Narrow, asymmetric for small roads and walkways.
• Type III: Wide, asymmetric for larger streets.
• Type IV: Forward-throw for intersections and wide roadways.
• Applications: City streets, highways, residential roads.

Post Top Lighting

• Description: Decorative lighting mounted on posts for public spaces.
• Preferred Distribution Types:
• Type V: Symmetrical, circular for even illumination in all directions.
• Type VS: Symmetrical square for uniform lighting in plazas and gardens.
• Applications: Parks, sidewalks, urban plazas.

Parking Lot Lighting

• Description: Enhances safety and visibility for vehicles and pedestrians.
• Preferred Distribution Types:
• Type III: Wide coverage for large parking areas.
• Type IV: Forward-throw for perimeter lighting.
• Type V: Circular pattern for central zones.
• Applications: Shopping malls, commercial parking lots, airport parking.

Sports Lighting

• Description: High-powered lighting for sports fields and stadiums.
• Preferred Distribution Types:
• NEMA Types³ 1–3: Narrow beams for tall poles and focused illumination.
• NEMA Types 4–6: Medium to wide beams for larger fields.
• Applications: Football fields, tennis courts, multi-sport arenas.

Flood Lighting

• Description: Powerful luminaires used for large outdoor spaces and architectural highlights.
• Preferred Distribution Types:
• NEMA Types 2–6: Ranges from narrow to wide beam spreads.
• Type IV: Asymmetric forward-throw for controlled area lighting.
• Applications: Stadiums, industrial zones, building facades, event spaces.

Selecting the right lighting distribution¹ ensures safety, efficiency, and the best visibility for outdoor applications. Properly chosen light distributions reduce energy consumption and improve functionality.

Conclusion

Choosing the right LED light distribution is essential for achieving the best illumination, safety, and energy efficiency. Understanding IESNA distribution types⁴, BUG ratings, and NEMA classifications ensures that your lighting design meets both functional and aesthetic needs.

Whether lighting streets, sports fields, or building facades, selecting the right distribution pattern makes all the difference in performance and visual comfort. If you need help choosing the best lighting solution for your project, feel free to contact us. We’re here to help.

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