Evaluating the photometric performance of high-power sports luminaires requires looking beyond raw lumen output or simple wattage ratings. In modern athletic field engineering, Horizontal Illuminance (Eh) and Vertical Illuminance (Ev) represent the two foundational parameters that dictate whether a stadium floodlighting system merely illuminates the ground or delivers a crisp, three-dimensional visual environment suitable for high-speed competition and 4K Ultra-HD television broadcasting.
1. Defining Eh and Ev: Status and Purpose in Floodlight Engineering
Understanding how light vectors interact with human eyes and digital camera sensors begins with establishing the physical definition and technical hierarchy of horizontal versus vertical light planes.
1.1 Distinguishing Between Horizontal and Vertical Light Planes
Horizontal Illuminance (Eh) measures the total luminous flux falling per unit area onto a flat, horizontal surface—typically the turf, hardwood court, or track surface at ground level (z = 0). It serves as the baseline parameter establishing overall field brightness, playing surface color rendering, and general background contrast for athletes on the field.
Conversely, Vertical Illuminance (Ev) measures luminous flux impinging upon a vertical plane situated perpendicular to the playing field. In modern stadium design, Ev has risen to equal—and often superior—status compared to Eh. Vertical illuminance is critical because human beings, flying balls, and television cameras view athletes primarily from the side. High Ev reveals facial features, eliminates harsh neck shadows, reveals three-dimensional muscular movement, and provides camera sensors with the photon density needed for high-frame-rate slow-motion tracking.
1.2 Mathematical Derivations Governing Eh and Ev Calculation
In photometric ray-tracing, the relationship between horizontal and vertical illuminance is directly controlled by the aiming angle (θ) of the high-mast floodlight relative to the vertical axis.
1. Horizontal Illuminance Formula:
Eh = ( Iθ × cos θ ) / d²
Where Iθ is the luminous intensity in candelas at angle θ, and d is the distance from the floodlight to the field grid point.
2. Vertical Illuminance Formula:
Ev = ( Iθ × sin θ ) / d²
Where sin θ isolates the vector perpendicular to the ground plane, facing specific camera orientations or athlete visual horizons.
3. The Illuminance Proportionality Ratio (Ev / Eh Balance):
Ratio = Ev / Eh = tan θ
To avoid extreme facial shadowing while maintaining strong ground contrast, international broadcast specifications dictate that the ratio must remain within 0.75 ≤ Ev / Eh ≤ 1.25 across all primary camera viewing vectors.
2. The Application and Functional Roles of Eh and Ev Across 6 Venue Types
With the fundamental vector formulas established, we can analyze how optical designers manipulate Eh and Ev parameter targets to satisfy the functional demands of specific athletic environments.
2.1 Football Stadium Lighting (Outdoor Soccer Pitch)
On a vast outdoor football pitch (105m × 68m), main broadcast cameras (Cam 1 and Cam 2) operate from elevated side gantries, demanding high vertical illuminance directed specifically toward the main camera axis (Evma).
While Eh ensures the green grass turf is rendered vividly, a robust Ev (typically ≥ 1400 lux for HDTV) is mandatory so that high-speed long passes and air duels remain fully visible. Without sufficient Ev, players appear as flat silhouettes against a bright grass background.
2.2 Indoor Basketball Court Lighting
Indoor basketball involves frequent vertical head movement as players track high rebounds, requiring floodlights to project vertical illuminance onto four surrounding quad-planes without causing direct glare.
Engineers maintain high Ev levels (≥ 1000 lux) along the key area and baseline zones using asymmetric reflectors mounted along court boundaries. This ensures that camera angles placed courtside capture clean three-dimensional lighting on athletes driving to the basket while keeping glare ratings low (UGR ≤ 19).
2.3 Tennis Court Lighting
Because a tennis ball travels at speeds exceeding 200 km/h across flat trajectories, vertical illuminance along the net plane directly dictates player reaction times.
Floodlight layouts on tennis courts must project uniform Ev from side-mounting poles to illuminate both sides of the ball in flight. If Eh is high but Ev is neglected, the tennis ball becomes visually dark as it crosses the net plane, degrading athlete response speeds.
2.4 Badminton Court Lighting
Badminton represents an extreme case where shuttlecocks spend a majority of play time high above ground level, shifting primary importance away from Eh toward vertical and spatial air-volume brightness.
To prevent players from being blinded when gazing upward, high Ev must be generated through indirect floodlight distribution or side-mounted asymmetric luminaires. This creates a bright, highly visible vertical contrast plane against the darker ceiling backdrop.
2.5 Swimming Center Lighting (Specular Water Control)
Aquatic facilities require careful balance between water-surface Eh and above-water Ev to prevent specular reflection blinding judges and overhead cameras.
Floodlights mounted along perimeter maintenance bridges project light at glancing angles (≤ 50° relative to vertical normal), driving vertical illuminance across emerging swimmers' heads and arms while preventing high horizontal spot reflections on the water surface.
2.6 Track & Field Stadium Lighting
Because track events involve sprinters running toward specific camera finish lines, vertical illuminance must remain constant along 360 degrees of the oval track.
High-mast floodlight towers positioned at four corners must generate overlapping light cones. This ensures that as runners move around curve sectors, their chest bib numbers and faces maintain stable Ev values without flickering as they pass under successive light towers.
Eh vs. Ev Functional Metrics Engineering Table
| Venue Type | Primary Purpose of Eh | Primary Purpose of Ev | Target Ev / Eh Ratio | Critical Camera Angle |
|---|---|---|---|---|
| Football Field | Turf brightness & ground ball contrast | 3D player modeling & slow-motion tracking | 0.75 ≤ Ratio ≤ 1.0 | Main Side Stand (Cam 1) |
| Basketball Court | Hardwood surface glare control | High rebound visibility & courtside camera fill | 0.80 ≤ Ratio ≤ 1.1 | Baseline & High Center Cam |
| Tennis Court | Court line boundary visibility | High-speed ball tracking along net plane | 0.70 ≤ Ratio ≤ 0.9 | Baseline Extended Vector |
| Badminton Court | Floor outline definition | Shuttlecock high-altitude trajectory contrast | 0.85 ≤ Ratio ≤ 1.2 | Side-Court Angle |
| Swimming Center | Lane line submerged recognition | Facial feature rendering above water splash | 0.75 ≤ Ratio ≤ 1.0 | Side-Deck Bridge Cam |
| Track & Field | Oval running lane continuity | Finish line chest-bib photo-finish capture | 0.70 ≤ Ratio ≤ 0.95 | Finish Line Straightaway |
3. Global Standard Benchmark: Eh / Ev Provisions in JGJ 153, IES RP-6, and EN 12193
Evaluating global engineering frameworks demonstrates how regional codes prioritize horizontal versus vertical illuminance balances for televised events.
3.1 Cross-Regional Provisions for Vertical Vector Ratios
International standards handle vertical illuminance with subtle regulatory nuances:
China JGJ 153-2016: Mandates explicit minimum limits for main camera vertical illuminance (Evma) and auxiliary camera vertical illuminance (Evac), requiring Ev / Eh ≥ 0.75 for HDTV broadcast classes (Class V/VI).
North America IES RP-6: Expresses illuminance targets in foot-candles, specifying vertical camera fill requirements directly based on distance from sideline broadcast trucks to the field center line.
Europe EN 12193 & FIFA Stadium Guidelines: Enforces strict vertical illuminance uniformities (U1v ≥ 0.6, U2v ≥ 0.7) and dictates that vertical light levels facing 4K cameras must remain flicker-free with TLCI ≥ 85.
4. Optical Lens Engineering: How Modern Floodlights Achieve Target Ev / Eh
Converting electrical power into precisely controlled horizontal and vertical light vectors requires sophisticated optical lens systems inside modern high-power LED floodlights.
4.1 Asymmetric Optical Dispersion & Aiming Angle Engineering
Legacy floodlights utilizing symmetrical round reflectors projected equal light cones in all directions, often generating high Eh directly under the pole while failing to project adequate Ev across the field center.
Modern LED sports floodlights employ Total Internal Reflection (TIR) asymmetric optical lenses. These customized TIR lenses refract beam distribution forward at precise tilt angles (e.g., 45° to 60° forward throw), converting horizontal luminous waste into concentrated vertical light facing stadium camera towers without requiring physical luminaire tilt angles that cause severe blinding glare.
5. Computer Optical Modeling & Field Measurement Protocols
Validating that a stadium floodlighting design satisfies target Eh and Ev ratios requires pre-construction digital simulation paired with post-installation field audit protocols.
In software platforms like Dialux evo or AGi32, calculation grids are established at ground level (z = 0) for Eh, and at vertical planes 1.0 meter or 1.5 meters above ground facing specified camera positions for Ev. During physical commissioning, calibrated illuminance meters equipped with cosine-corrected photocell heads are mounted horizontally and vertically on precision tripod jigs to verify compliance point-by-point.
6. Conclusion & CPS Lighting Engineering Advantage
Mastering Horizontal Illuminance (Eh) and Vertical Illuminance (Ev) is the defining benchmark that elevates basic field illumination into a world-class, TV-broadcast-ready stadium experience. Achieving the ideal Ev / Eh balance requires precision luminaire selection, customized asymmetric optics, and rigorous 3D optical layout design.
At CPS Lighting, our technical engineering team specializes in advanced stadium floodlighting design compliant with JGJ 153, IES RP-6, and FIFA broadcast standards. Utilizing our high-performance LED floodlights featuring customized asymmetric optical lenses, we deliver optimal Ev / Eh ratios, zero-flicker driver performance, and maximum energy savings for facilities worldwide. Contact our engineering team today for a comprehensive Dialux optical simulation for your project.