More brands from

Sports lighting: Key considerations for illuminating the field of play and the spectator zones


A crucial, yet often overlooked, element of a first-class sports venue is its lighting system.

 

A great lighting system does more than just illuminate the field of play. Among other things, it also makes stadium visitors generally comfortable in their surroundings and ensures a successful television broadcast for spectators watching at home.

 

But beyond those simple imperatives, sports lighting is a complex business. International, national, regional, and local competitions all have their different lighting requirements; practice sessions and recreational sports call for different lighting regimes than competitive and professional events do. A sporting facility’s capacity and the distances from which spectators are viewing the action also come into play in lighting. This variety of interests explains why the CEN Standards are organized into different so-called classes, classes that happen to be consistent with TV broadcasting standards.

Level of Activity

Class I

Class II

Class III

Inter- and National Competition
Regional Competition
Local Competition
Training
Recreational
Lighting classes according to CEN Standard
Given the many factors involved in providing excellent lighting at a sporting venue, it might be useful to define the key considerations that sports lighting professionals need to take into account.

Lighting the field of play

 

  • Horizontal illuminance

 

The illuminated playing surface takes up a major part of the field of view for anyone in a sporting venue, whether players, officials or spectators. Horizontal illuminance (Eh) represents the illuminance on this horizontal plane at ground level. It serves primarily to create a stable visual background against which the eye can discern players and objects.

 

For non-televised lighting classes, an average horizontal illuminance of between 50-100 lux and 750 lux is required, depending on the sport in question and on the lighting class. For televised competitions, the vertical illuminance level is more important than the horizontal illuminance level; to ensure that the television picture has a well-balanced brightness, the ratio between the average vertical and horizontal illuminance should match as closely as possible, but shouldn’t exceed a 0.5 to 2 ratio. The horizontal illuminance shouldn’t be less than half the vertical illuminance or greater than twice the vertical illuminance.

 

  • Vertical illuminance

 

The athletes in any particular sporting event, as well as the ball they’re using, can be understood as vertical surfaces. This means that we need to keep vertical illuminance (Ev) primarily in mind when we light them.

 

To guarantee an optimal view and make it possible for the human eye to identify players from every direction, we should generally measure Ev at a height of 1.5 meters, which corresponds approximately to the faces of the players.

 

Experience shows that there’s an intimate relationship between vertical and horizontal illuminance. For sports with no specific vertical illuminance criteria, vertical illuminance will be sufficient if the required horizontal illuminance is achieved, and if the lighting design rules are followed.

 

Televised events involve exceptions to this rule of thumb; vertical illuminance has a major influence on the quality of a final television or film picture. Television broadcasting generally calls for an average Ev of between approximately 1000 lux and 2000 lux.

 

  • Uniformity

 

Ensuring uniformity is important in avoiding adaptation problems for both players and spectators. If uniformity is inadequate, certain objects or player details might be difficult to see from certain positions.

 

Uniformity is expressed as

  • the ratio of the lowest to the highest illuminance (U1 = Emin/Emax)
  • the ratio of the lowest to the average illuminance (U2  = Emin/Eaverage)

 

In non-televised situations, the uniformity of the horizontal illuminance is generally specified as between 0.5 to 0.7 (Emin/Eaverage) depending on sport and lighting class.

 

In televised situations, high uniformity is necessary for smooth and natural-looking scenes, especially in this era of HDTV; horizontal illuminance is generally 0.8, whereas vertical illuminance in the direction of fixed cameras requires a uniformity value of 0.7 (Emin/Eaverage).

 

Even when the uniformity ratios as we’ve defined them are acceptable, changes in illuminance can be disturbing if they happen too quickly. This problem is most likely to arise when a television camera pans. The illuminance uniformity for TV/film coverage at a certain grid point thus has to be expressed as a percentage change from the average adjacent grid points. This is called the uniformity gradient.

 

A common uniformity gradient value for both horizontal and vertical illuminance in the direction of main cameras of ≤20% on a 4m calculation grid might ensure smooth panning between one area to another.

 

  • Glare restriction

 

Glare is a subjective factor for which CIE has, on the basis of extensive field research, developed a practical evaluation system for use in outdoor sports applications (CIE 112 Glare evaluation system for use within outdoor sports and area lighting).

 

CIE 112 defines a so-called glare rating factor (GR) ranging from 10 to 90 on the assessment scale. The lower the glare value, the better the glare perception for the players in a sporting event.

 

A maximum GR value of 50 is generally specified for sports projects.

 

  • Modelling and shadows

 

Modelling refers to lighting’s ability to reveal form and texture. Modelling ability is particularly important in providing a pleasant overall impression of the athletes and objects in the field of play, not to mention of the spectators in the stands. An installation where light comes from only one direction will result in harsh shadows and poor modelling.

 

  • Color properties

 

The color properties of luminaires have two important aspects:

  • The color appearance of the light. This is the color impression of the total environment that the light source creates.
  • The color rendering properties of the light source used, or the CIE Color Rendering Index (CRI). This describes how faithfully a light source can reproduce a range of colors.

 

An indication of a lamp’s color appearance can be obtained from its correlated color temperature as measured in degrees Kelvin (K), which vary mainly between 2000 and 6500K. The lower the color temperature, the "warmer" the color impression of the light is; the higher the color temperature, the "cooler" or more bluish the impression of the light is.

 

Sports lighting generally requires a color temperature of between 4000 and 6500 K.

 

The color rendering properties of a light source can be indicated by its Color Rendering Index, expressed as a numerical value between 0-100. A light source with a CRI of 100 will represent scene colors faithfully, with daylight as the standard of comparison. Color perception is highly relevant in most sports applications.

 

While some of the color distortions that artificial lighting causes are acceptable for non-televised activities, TV broadcasting requires highly accurate color rendition.

 

The transition from conventional lighting to LED lighting gave rise to a discussion of whether CRI remains the correct color fidelity metric for television broadcasting. It was developed based on the human eye response curve and for a set of pastel colors, and isn’t necessarily appropriate for sports broadcast cameras that transmit images rich in saturated colors.

 

The European Broadcasting Union (EBU) has developed the Television Lighting Consistency Index (TLCI), which is based on camera response. TLCI is gaining popularity among broadcasters as a color metric specifically designed for their needs. Discussion of this topic is ongoing, but there’s a general consideration that it should be easy to get colors right with a TLCI>80.

 

  • Flicker

 

A particular problem for super slow-motion cameras is a 50Hz flicker, due to the phasing of the light.

 

Cameras perceive light level changes due to the uneven ratio between the camera scanning frequency and the alternating amplitude of artificial lights powered by mains frequency. 

This effect, which is visible only during slow-motion replay, is called the flicker effect.

 

Sports federations have started to incorporate a so-called flicker factor into their lighting recommendations. To avoid any visible slow-motion image flicker, a flicker factor of less than 3 percent is recommended.

Atletico Malaga Koke

Safety lighting for participants

 

European norm EN 12193 requires that certain sporting events that might prove dangerous to continue in the absence of lighting be suspended to ensure participant safety.

 

The lighting level for use during the stoppage of an event is a percentage of the level for that class (5 percent or 10 percent*). Safety lighting is to come into play when the general lighting fails and there’s a power shortage for at least the period of time that the norm specifies. (This can be 30, 60, or 120 seconds, depending on the sport.)

 

The sports in question are swimming, indoor gymnastics, indoor and outdoor equestrian sports, speed skating, bobsledding and tobogganing, ski jumping, Alpine skiing, and bicycle racing.

Continuity lighting

 

Given the capital-intensive nature of professional sports and television coverage, it’s crucial that sports federations or organizing committees ensure an event’s continuity even if a power failure occurs.

 

It’s therefore a requirement at the majority of professional competitions that a primary power supply disruption automatically trigger a secondary power supply in a way that creates no disruption to the lighting of the field of play.

 

The main points to consider are these:

  • The time delay involved in switching from one power source to another, taking into account luminaires’ re-strike times.
  • The need to maintain a lighting level sufficient to maintain broadcasting continuity.

 

Sports federations or organizing committees usually define these criteria.

Lighting the spectator areas

 

Adequate horizontal illuminance is key to ensuring spectators’ safety of movement as they enter or leave the stands and other premises.

 

For safety purposes, and to make it possible for spectators to orient themselves effectively, a stadium must be equipped with an emergency lighting system approved by relevant local authorities for use in the event of a general lighting failure in any part of the stadium to which the public or staff have access.

 

EN1838 for emergency lighting is relevant here. In addition, European norm EN 12193 recommends a minimum value of 10 lux in the spectator area, to ensure spectator comfort.

Spectator area lighting during TV broadcasts

 

It can happen that, to suit its production style, a TV broadcaster will specify a spectator-area lighting level as a ratio of the field of play lighting level.

 

If dedicated luminaires are being used to illuminate areas for spectators, they should have a color temperature that matches as closely as possible the color temperature of the field of play’s lighting. The flicker factor should also be similar to that of the field of play’s lighting.

Controlling spill light

 

Stray light from outdoor lighting installations can disturb people in the vicinity: drivers on adjacent roads, for example, and inhabitants of nearby houses. Local authorities or municipalities sometimes maintain their own guidelines on such matters.

 

Where no guidelines exist, European norm EN 12193 has defined obtrusive light limits based on CIE recommendations. The key criteria here are vertical illuminance on properties, the luminaire intensity in a potentially obtrusive direction of each light source, the quantity of light emitted above the horizontal plane that passes through the center of the luminaire, and the level of glare that area drivers experience.

The Signify advantage

 

The right sports lighting solution will take into account these different considerations.

 

Philips ArenaVision LED floodlighting system from Signify, designed dedicatedly for sports and entertainment venues, for example, is flicker-free and offers light color properties adapted to the latest broadcasting standards, as well as ultra-efficient optics for maximum design flexibility and the production of the best-quality and most uniform light. Its full controllability lets professionals speedily and flexibly create dynamic lighting scenes, or to create the right atmosphere. In addition, when connected to Interact Sports Lighting management software, ArenaVision LED offers remote diagnostics and management and can interface with building management systems.

 

The Philips OptiVision LED floodlighting system, Signify’s area and recreational sports lighting solution, can also be the right choice. It offers a wide choice of light distributions to cover any positioning configuration, providing excellent uniformity. The light control enabled by its asymmetrical light distributions cuts down on glare, and the system can be accessorized to drastically reduce spill light.

 

In addition, when connected to Interact Sports’ software designed for recreational and training field illumination, OptiVision LED improves operational efficiency by giving users the capacity to monitor the lighting installation. And it offers further comfort and cuts operational costs by offering a set of pre-programmed light scenes to choose from depending on user needs.

 

Both luminaries, meanwhile, offer an instant on-off feature that’s critical in providing lighting continuity.

 

The right sports lighting system answers a range of needs: to ensure broadcast quality, to keep spectators and players safe, to guarantee great playing conditions, to minimize unwanted effects for area residents, and more. Signify is at the forefront in providing systems that cover this challenging range.