Glare Rating (GR) for Sports Lighting: ANSI/IES Calculation, Specification, and Validation

An engineering reference for facility designers, electrical engineers, and procurement teams specifying LED sports lighting glare performance. Covers the ANSI/IES Glare Rating calculation, target values by play tier, and how to specify and validate GR in a photometric study.

Glare Rating (GR) is the IES RP-6–required quantitative measure of disability and discomfort glare from a sports lighting installation. Most bids skip the GR calculation entirely — which means most installations are not technically validated against the standard they claim to meet. This guide covers what GR measures, how it’s calculated, target values by tier, and how to specify it in a bid.

What Glare Rating Measures

Glare Rating quantifies the visual impact of bright light sources within a viewer’s field of view. Two glare types contribute:

·Disability glare — measurable reduction in visual acuity from light directly entering the eye

·Discomfort glare — subjective visual fatigue and squinting accumulated over a session

GR captures both as a single numeric value, calculated at viewing positions across the playing area (player eye height, fielding positions, broadcast camera positions).

The GR Calculation Inputs

Glare Rating per ANSI/IES standards is calculated from:

1.Luminance of each fixture as seen from the viewing position

2.Angular position of each fixture in the viewer’s field of view

3.Background luminance at the viewing position

4.Solid angle subtended by each fixture from the viewing position

The calculation produces a numeric GR value typically in the range 20–80, with lower values indicating less glare. AGi32 and DIALux software calculate GR automatically from the fixture array geometry and photometric data.

GR Target Values by Tier

IES RP-6 specifies these targets by class. Class I (FBS, MLB, FIFA) targets GR <30. Class II (NCAA D-I, FCS, USL, MiLB) targets GR <40. Class III (HS varsity, NCAA D-III) targets GR <45. Class IV/V targets GR <50.

Why Most Bids Skip GR Calculation

Three reasons bidders omit GR from photometric deliverables:

5.Cost — GR calculation requires the AGi32/DIALux model to include viewing positions and background luminance, which adds modeling time

6.Risk — the GR result may exceed the target, requiring layout or fixture changes

7.Buyer ignorance — many bid evaluators don’t know to ask for it

The result: photometric studies that show the foot-candle and uniformity targets but ignore the glare side of the spec. Specifying GR explicitly in the bid forces bidders to validate the full IES RP-6 compliance picture.

How Layout Drives GR

GR is driven by four design variables, in order of impact:

8.Mounting height — higher mounting reduces fixture luminance from viewing positions and lowers GR

9.Fixture aiming — cross-aimed fixtures pointing across the field have lower GR than fixtures aimed straight down the foul line

10.Optical control — full cut-off, indirect asymmetric optics produce lower GR than direct-flood optics

11.Player sightline avoidance — no fixture in the batter’s, kicker’s, or QB’s sightline cone

Layout-driven GR control is significantly more effective than fixture-level shielding. A taller pole with full cut-off, indirect asymmetric optics produces lower GR than a shorter pole with shielded direct-flood fixtures.

GR Validation in the Photometric Study

Required deliverables:

·GR value calculated at every primary viewing position (player eye height, fielder positions, broadcast camera positions where applicable)

·GR map across the playing area showing where the highest GR values occur

·Identification of any specific fixtures that contribute disproportionately to GR

·Mitigation recommendations if any GR value exceeds the class target

Sport-Specific GR Considerations

How to Specify GR in a Bid

Standard language:

“Photometric study deliverable shall include Glare Rating (GR) calculation per ANSI/IES standards at all primary viewing positions for [sport]. GR shall not exceed [target value per class] at any specified viewing position. GR map across the playing area shall be provided. If any GR value exceeds the target, mitigation strategies shall be presented for review.”

Tighter target language for high-end broadcast:

“GR ≤ 35 at all primary viewing positions including broadcast camera positions, validated in AGi32 (or equivalent) photometric study with viewing-position-specific calculation. Camera-position GR validation required for sideline, end-zone, and skycam camera locations.”

Common GR Specification Errors

·Specifying foot-candles and uniformity but omitting GR

·Approving a photometric study that doesn’t include GR calculation

·Using a single GR value across the field instead of viewing-position-specific

·Missing GR validation at broadcast camera positions for streaming/broadcast venues

·Permitting GR >50 in a competition-tier specification

·Specifying GR but not requiring viewing-position documentation

Duvon’s GR Performance

Duvon photometric studies include GR calculation at all primary viewing positions for the relevant sport. Typical GR results for Duvon installations:

The full cut-off, indirect asymmetric optics standard across the Duvon line drives lower GR results than equivalent direct-flood fixtures because light is redirected across the play surface rather than projected into player sightlines.

For broader IES standards, see IES RP-6 Sports Lighting Standards. For BUG ratings, see BUG Rating System Explained. For dark-sky compliance, see Dark-Sky Compliant Sports Lighting.

Validating GR for a project? Request a free 24–48 hour AGi32 photometric study with full Glare Rating documentation →

Frequently Asked Questions

What is Glare Rating (GR) for sports lighting?

Glare Rating per ANSI/IES standards quantifies disability and discomfort glare from a sports lighting installation. It’s calculated at viewing positions across the playing area (player eye height, broadcast camera positions) using fixture luminance, angular position, background luminance, and solid angle subtended. AGi32 and DIALux calculate GR automatically from the fixture array geometry.

What GR target should I specify for HS varsity sports lighting?

HS varsity (IES Class III) targets GR < 45. NCAA D-II/III also targets GR < 45. Tighter targets apply to higher classes: GR < 40 for NCAA D-I (Class II broadcast), GR < 35 for FBS/Pro broadcast (Class I), GR < 50 for recreational (Class IV/V). Values > 60 are non-compliant with IES RP-6 at any class.

Why do most sports lighting bids skip Glare Rating?

Three reasons: (1) GR calculation adds photometric modeling time and cost; (2) the GR result may exceed the target, requiring layout or fixture changes; (3) many bid evaluators don’t know to require it. Specifying GR explicitly in the bid forces bidders to validate the full IES RP-6 compliance picture, not just foot-candles.

How do I lower GR in a sports lighting design?

Four design variables, in order of impact: (1) Increase mounting height — higher mounting reduces fixture luminance from viewing positions; (2) Cross-aim fixtures across the field rather than down the foul lines; (3) Specify full cut-off, indirect asymmetric optics that redirect light across the play surface; (4) Avoid placing fixtures in player sightline cones (batter, QB, kicker, goalkeeper).

How do I specify GR in a sports lighting bid?

Standard language: “Photometric study deliverable shall include Glare Rating (GR) calculation per ANSI/IES standards at all primary viewing positions for [sport]. GR shall not exceed [target value per class] at any specified viewing position. GR map across the playing area shall be provided. If any GR value exceeds the target, mitigation strategies shall be presented for review.”

What GR do Duvon sports lighting fixtures typically achieve?

Apex Series broadcast installations typically deliver GR 25–32. Vanguard NCAA/FCS/USL installations deliver 30–38. Liberty HS varsity installations deliver 35–42. Freedom tournament court installations deliver 30–38. The full cut-off, indirect asymmetric optics standard across the Duvon line drives lower GR than direct-flood fixtures because light is redirected across the play surface rather than projected into player sightlines.