Professional Engineering Series

How to Read a Sports Lighting Photometric Report (AGi32): A Step-by-Step Engineer’s Breakdown

How to Read a Sports Lighting Photometric Report (AGi32): A Step-by-Step Engineer’s Breakdown

Interpreting Foot-Candles, Uniformity, Vertical Illuminance, and Spill Light to Verify Real-World Performance

Why Photometric Reports Matter

A photometric report is the only document that predicts how a lighting system will perform before it is installed. It translates design assumptions into measurable outcomes:

  • Light levels across the field

  • Uniformity of distribution

  • Visibility conditions for players

  • Impact beyond the property line

If you cannot read the report, you cannot verify the system.

What an AGi32 Report Actually Contains

A complete AGi32 sports lighting report typically includes:

  • Site layout with pole locations

  • Fixture schedule and aiming directions

  • Horizontal illuminance grid

  • Vertical illuminance grid

  • Uniformity summary

  • Spill light / property line analysis

Each section answers a different performance question.

Step 1: Start with the Summary Metrics

At the top of the report, you will find:

  • Average foot-candles

  • Minimum foot-candles

  • Maximum foot-candles

  • Uniformity ratios

These numbers define whether the system meets basic requirements. However, they do not tell the full story.

Step 2: Read the Horizontal Illuminance Grid

The horizontal grid shows light levels across the playing surface.

What to look for:

  • Consistency across all zones

  • No significant dark areas (low minimum values)

  • No excessive hotspots (high maximum values)

Common mistake:

  • Focusing only on average foot-candles instead of distribution.

Step 3: Check Uniformity Ratios

Uniformity is typically expressed as:

  • Max:Min

  • Min:Avg

Target ranges depend on the application, but lower ratios indicate better consistency.

Warning signs:

  • Large gaps between max and min values

  • Uneven distribution across key play areas

Uniformity directly affects visual comfort and performance.

Step 4: Analyze Vertical Illuminance (Most Important Step)

Vertical grids show how well players can see:

  • Ball movement

  • Opponents

  • Depth and motion

What to look for:

  • Adequate vertical levels across key heights

  • Consistent values across the field

  • No major drop-offs in critical zones

If vertical data is missing, the report is incomplete.

Step 5: Review Fixture Layout & Aiming Diagrams

The report should include:

  • Pole locations

  • Fixture orientation

  • Aiming angles

This explains how the lighting system is physically delivering light.

Warning signs:

  • Fixtures aimed directly toward player sightlines

  • Over-reliance on a single direction

  • Lack of cross-lighting

Aiming is where most designs succeed or fail.

Step 6: Evaluate Spill Light & Property Line Data

Photometric reports extend beyond the field to show:

  • Light levels at property boundaries

  • Impact on surrounding areas

Check for:

  • Compliance with local limits (often 0.0–1.0 fc)

  • Smooth drop-off outside the playing area

Excessive spill light leads to complaints and permit issues.

Step 7: Identify Glare Risk (Indirect Indicators)

Glare is not always listed as a single value, but it can be identified through:

  • High-intensity zones near player sightlines

  • Steep aiming angles

  • Concentrated light at high angles

If light appears “clustered” or overly directional, glare risk is high.

Step 8: Compare Against Requirements

The report should be evaluated against:

  • IES lighting class targets

  • Project-specific specifications

  • Zoning and spill light requirements

If the report does not clearly align with these, performance is uncertain.

Step 9: Look for Over-Design or Under-Design

Over-designed systems:

  • Excessive foot-candles

  • Higher cost and energy use

  • Increased glare

Under-designed systems:

  • Low minimum values

  • Poor uniformity

  • Inadequate vertical lighting

The goal is optimized—not maximized—performance.

Step 10: Verify the IES Files and Assumptions

Every report is only as accurate as its inputs.

Check for:

  • Verified IES photometric files

  • Realistic mounting heights

  • Accurate pole locations

Incorrect inputs lead to misleading results.

Indirect Asymmetric Optics (What to Look For in the Report)

When indirect asymmetric systems are used correctly, the report will show:

  • Strong vertical illuminance distribution

  • Smooth uniformity across the field

  • Lower high-angle intensity

  • Reduced spill light beyond boundaries

These characteristics indicate efficient and controlled lighting.

Common Red Flags in Photometric Reports

  • No vertical illuminance data

  • Unrealistic uniformity values

  • Extremely high average foot-candles

  • No property line analysis

  • Missing aiming diagrams

These indicate incomplete or unreliable designs.

How to Use the Report in Procurement

A photometric report should be used to:

  • Compare competing designs

  • Validate compliance before purchase

  • Require equivalent performance in substitutions

This shifts evaluation from price to verified performance.

Conclusion

A photometric report is not a technical formality—it is the most important document in a sports lighting project. It defines whether the system will perform as intended, meet regulatory requirements, and deliver consistent visibility.

By understanding how to read horizontal and vertical data, evaluate uniformity, and assess spill light and glare, decision-makers can eliminate uncertainty and select lighting systems based on proven performance.

For modeling methodology, see AGi32 Sports Lighting Design Guide. For validation principles, refer to Photometric Analysis for Sports Fields.