What does light distribution mean for an LED luminaire?

Light distribution describes how luminous intensity is directed at different angles around a luminaire. It affects coverage, spacing, uniformity, glare and spill light even when two fixtures have the same wattage or lumen output.

What is the difference between IES Type I and Type V distribution?

Type I is a narrow, elongated roadway pattern commonly associated with paths or narrow routes and central placement. Type V is approximately symmetric around the luminaire and is used for open areas with central mounting. The final application still requires a photometric calculation.

Does IES Type IV mean a high-output luminaire?

No. Type IV describes a plan-view distribution with strong forward throw from an edge or perimeter position. It does not define wattage, lumen output or product quality.

What does a NEMA beam spread number represent?

The NEMA number identifies a field-angle range measured at 10% of maximum candela. Class 1 covers 10° to 18°, while Class 7 covers 130° and above. An asymmetric code lists horizontal spread first and vertical spread second.

Are beam angle and NEMA field angle the same?

Not necessarily. Product beam angle is commonly reported at 50% of maximum intensity, while NEMA spread uses the 10% field-angle boundary. Buyers should confirm which threshold a catalog value uses before comparing optics.

Is Type V automatically suitable for stadium lighting?

No. Stadium systems normally combine several narrow, medium, wide or asymmetric floodlight optics aimed at different field zones. Uniformity, glare, vertical illuminance and spill light must be verified through simulation and field commissioning.

What information should a buyer request before selecting an LED optic?

Request the IES or LDT photometric file for the exact model and optic, together with mounting and aiming information. Use those data in a project model and compare maintained illuminance, uniformity, glare and boundary spill before ordering.

Light Distribution Types for LED Lighting: IES and NEMA Guide

2024-05-21

Contents

1. Why Distribution Matters More Than Wattage

2. IES Type I to Type V Roadway Patterns

3. NEMA Beam Spread Classifications

4. Why Stadium Optics Need a Different Approach

5. Reading Photometric Data Before Ordering

6. A Practical Distribution Selection Workflow

7. Technical Sources

1. Why Distribution Matters More Than Wattage

A luminaire’s wattage and lumen output do not show where the light will land. Light distribution types describe the angular pattern of luminous intensity. That pattern controls pole spacing, target illuminance, uniformity, glare and spill light. Two fixtures with the same wattage can produce very different results when their optics send candela in different directions.

For wholesalers and project buyers, the useful question is not “Which distribution is best?” but “Which distribution matches the mounting geometry and calculation target?” A roadway, parking perimeter and football pitch use different optical logic. Current options should therefore be checked against the photometric files available through the CPS Lighting product center, not selected from wattage alone.

Roadway lighting distribution from LED street lights — Roadway distribution in practice

2. IES Type I to Type V Roadway Patterns

ANSI/IES RP-8 uses Type I to Type V to describe plan-view roadway and parking distributions relative to the luminaire and mounting height. These types are not brightness grades. Type IV does not mean “high output,” and Type V does not automatically mean “stadium lighting.” They describe the shape and principal direction of the candela distribution.

IES type	Plan-view characteristic	Typical layout context
Type I	Narrow, elongated two-way pattern	Paths or narrow routes with central placement
Type II	Moderate transverse reach	Wider paths and relatively narrow roadways
Type III	Broader transverse reach	Roadways and parking-area rows
Type IV	Strong forward throw from one side	Perimeter or edge-mounted area lighting
Type V	Approximately symmetric around the luminaire	Open areas with central mounting

Roadway data may also use very short, short, medium, long and very long longitudinal classifications. These relate the maximum-intensity location to mounting height; they are not guaranteed illumination distances. Pole setback, tilt, pavement width and the complete IES file still determine actual coverage.

3. NEMA Beam Spread Classifications

A NEMA beam spread classifies a floodlight’s horizontal and vertical field angles at 10% of maximum candela. This is different from a catalog beam angle commonly measured at 50% of maximum intensity. For an asymmetric designation, the horizontal value comes first. NEMA 7H × 6V therefore identifies angular ranges, not exact angles of 120° by 90°.

NEMA class	Field-angle range	Relative spread
1	10° to 18°	Very narrow
2	18° to 29°	Narrow
3	29° to 46°	Medium narrow
4	46° to 70°	Medium
5	70° to 100°	Medium wide
6	100° to 130°	Wide
7	130° and above	Very wide

4. Why Stadium Optics Need a Different Approach

A sports field is not designed by assigning one roadway type to every stadium flood light. High-mast layouts normally combine narrow, medium, wide and asymmetric optics. Far-side targets need concentrated candela, while near-side zones need wider coverage. Beam overlap controls uniformity, but excessive overlap raises glare, spill light and connected load.

CPS reports an 18 m high-pole layout and more than 550 lx average illuminance for its Grade III football field project. The public case does not publish NEMA codes, so none should be inferred. It demonstrates why mounting geometry and measured results matter more than a generic distribution label. CPS discusses this workflow further in its stadium retrofit distribution guide.

LED stadium lighting with overlapping optical distributions — Overlapping stadium optical distributions

5. Reading Photometric Data Before Ordering

Distribution labels are screening tools. The purchase decision should use an IES or LDT photometric file measured for the exact model and optic. Check the polar or Cartesian candela plot, peak intensity direction, horizontal and vertical field angles, zonal lumens and any BUG rating. The IES explains that goniophotometry measures intensity at many angles and stores those data for calculation.

Next, model the real pole coordinates, mounting heights, aiming angles, target grid and obtrusive-light boundaries. A DIALux and AGi32 photometric simulation can compare illuminance, uniformity, glare and spill before hardware is ordered. This is where an optic either proves its suitability or fails it.

6. A Practical Distribution Selection Workflow

Start with the site geometry and task: road width, setbacks, field dimensions, camera directions and property boundaries. Define maintained illuminance, uniformity, glare and spill limits. Shortlist distributions using the appropriate IES roadway type or NEMA spread, then request the exact photometric file rather than relying on a product-family brochure.

Finally, simulate several optic combinations, check pole and bracket constraints, and commission the installed aiming on site. If nearby properties are sensitive, review backlight, uplight and glare using the CPS BUG rating guide. The correct distribution is the one that meets the verified project criteria with acceptable glare, spill, energy and installation cost.

7. Technical Sources

1. ANSI/IES RP-8-22: roadway and parking lighting

2. IES: photometric files and goniophotometry

3. Hubbell Lighting: NEMA beam spread ranges

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Core Keywords:

light distribution types, IES Type I to Type V, NEMA beam spread, LED roadway lighting, stadium flood light optics, photometric IES files, DIALux lighting simulation, anti-light spill control, sports lighting supplier