Several issues that need attention in stadium lighting design

In the design of Sports stadium lighting, the problems of sufficient illuminance and uniformity of lighting, sufficient brightness and glare-free lighting, proper shadow and color accuracy, and the influence of stroboscopic effect have been analyzed in detail, and the above problems must be understood. Only with mastery can lighting design be done well.

For a long time, many sports events have shown a worldwide tendency, which is why it has proved the urgent need for competition and training in the evening or evening. Therefore, Sports stadium lighting is an important content of stadium design and is more complicated. It not only needs to meet the requirements of athletes for competitions and audience viewing, but also to meet the requirements of lighting color temperature, illuminance, and uniformity of illuminance for filming and live TV broadcasting. This requirement is much higher than the requirements of athletes and audiences. Modern stadiums generally use high-power 1.8kW, 2kw metal halide lamps as light sources, which have high optical efficiency (about 80-100Lm/w), high color rendering, and color temperature between 5000-6000K, which can meet high-definition color TV Broadcasting (HDTV) requirements for outdoor lighting. For this reason, to do a good job in the design of modern Sports stadium lighting, designers must understand and master the following issues: there should be sufficient illuminance and uniformity of illuminance, brightness and glare-free lighting, appropriate shadow effects and correctness of colors , The influence of stroboscopic effect, etc.

1. Sufficient illumination

The brightness of the object is very important to the human visual impact, and it is also very important to the TV broadcast. Like the reflection of an object, its brightness is represented by the term "illuminance" that people don't often use. According to reports, the early flood lighting scheme used high-power incandescent lamps with an illuminance of about 150lx, which could meet the requirements of athletes and spectators under the conditions at the time. After the emergence of black-and-white TV broadcasting services, according to the requirements of TV broadcasting, it is necessary to increase the illuminance. The method is to increase the voltage of the incandescent lamp by 10%, or to replace the lighting source with a 1000W high-pressure mercury lamp. When the first method is used, the output power of the lamp can be increased by 35%, but the price paid is that the electricity load is increased, and the lamp life is reduced from 1000h to 250h; when the high-pressure mercury lamp is used, the illuminance can be increased by 50%. Without increasing electricity load.

Before the advent of color television broadcasting services, a horizontal illuminance of 200lx was sufficient. The output power of the entire Sports stadium lighting is about 250kw, which is generally used to increase the horizontal illumination to improve the performance of the lighting device. The increase in vertical illuminance is mainly to improve the visibility from the auditorium to the athletes.

In the 1990s, in domestic and international sports competitions held in many countries, television broadcasts required color. Color TV has higher requirements for lighting quality than black and white TV. International Sports Organization

Broadcasting and TV agencies have put forward the following requirements for stadium lighting installations:

(1) The minimum vertical illuminance required for the entire stadium is 800lx, and the illuminance should be from 1 to 1.5m above the ground plane and perpendicular to the plane where the main camera is located.

(2) For a closed lens with a long focal length, the required illuminance is not less than 1400lx. The illuminance necessary for color television broadcasting services. It also depends on the factors of the regional environment. Such as the degree of air pollution, it mainly determines the required picture quality, and picture quality is one of the main factors. Faster sports require a smaller aperture and higher illuminance of the camera lens. When the TV camera lens has a correspondingly smaller aperture, the super broadcast (that is, high-quality images) requires higher illuminance. The most commonly used color TV camera is a zoom lens. Normally, there is only an aperture of f: 2. When the large focal length can meet the needs of a certain sports game broadcast range, the number of apertures can also be increased. Therefore, when designing lighting, the designer should consider the aperture at least f:2.8 to f:4 or f:5.6, the most common lens aperture f:2 to f:5.6 required vertical illuminance value.

Color TV photography requires that the vertical illuminance be increased to 2000lx as much as possible. In fact, this value is subject to economic constraints and also limited by the glare caused by high illuminance.

The national sports industry standard TY/T1002.1-2005 "Sports Lighting Requirements and Inspection Methods Part 1: Outdoor Football Fields and Comprehensive Stadiums" stipulates that Outdoor football field lighting and comprehensive Sports stadium lighting standards.

2 The provisions of the vertical illuminance and its uniformity in the table refer to the main camera direction, and the auxiliary camera direction can be reduced by one level.

3Horizontal illuminance refers to the maintained average illuminance on the ground, and vertical illuminance refers to the maintained average illuminance in the direction of a 1.5M high vertical surface or the main camera.
 

4 The horizontal illuminance can be 0.5 to 2.0 times the vertical illuminance (0.75 to 1.5 times is recommended).
 

5 The illuminance values listed in the table can maintain the average illuminance value, and the maintenance factor is 0.8. For foggy and heavily polluted areas, this value can be reduced to 0.7.

2. Illumination uniformity

The uniformity of illuminance required for color photography is much greater than that of black-and-white photography or visual appreciation, both for horizontal illuminance and vertical illuminance. In the fast sports competition, in order to operate the camera without distorting the picture, the lighting needs to have high enough illuminance and good uniformity. The maximum brightness ratio between the brightest part and the darkest part of the main screen of color photography and videography cannot be greater than 40:1. The reflection and uniformity of illumination of different objects are the reasons for the brightness ratio. If the brightness ratio exceeds this value, a clear shadow or backlight phenomenon will appear, resulting in overexposure or underexposure, and color TV broadcasting will be distorted.
　　
The uniformity of illuminance uses a parameter to measure U1 and U2. U1 is the ratio of the minimum illuminance to the maximum illuminance in the stadium, namely U1=Emin/Emax; U2 is the ratio of the minimum illuminance to the average illuminance in the stadium, namely U2=Emin/Eave. Illumination uniformity can be divided into horizontal illuminance uniformity and vertical illuminance uniformity.

There are different vertical illuminances in different positions of the stadium playing field, which can cause confusion when shooting from a distance, especially when there is a fast sports game. The vertical illuminance uniformity on the plane facing the edge of the main camera or facing a fixed main camera position should be better than Evmin/Evmax=0.4. In the case of one or more main camera areas, meeting this requirement can be guaranteed, Sufficient illuminance can be obtained on the vertical plane facing the actual camera position of the area or areas. It can also ensure that the auxiliary camera shoots at any position in a limited area around the venue. In the end, satisfying these requirements also guarantees sufficient three-dimensionality for the athletes on the field.

A good horizontal illuminance uniformity is very important to avoid camera adjustment problems. The horizontal illuminance uniformity of the playing field should be better than Ehmin/Ehmax=0.5.

It is also very important that the horizontal illuminance does not change much at a certain distance. In order to have a suitable lighting gradient, the horizontal and vertical illuminance from a grid point to an adjacent grid point cannot exceed 20% of the grid point, and the ratio of the average horizontal illuminance to the average vertical illuminance must be between 0.5 and 2.0 .

In order to ensure the uniformity of the stadium's illuminance, the LED stadium lights installed on the 30-40m high light poles at the four corners of the venue and the light strip lights on the 20-30m high stand canopy need to be adjusted. The uniformity of illuminance is achieved by a certain number of adjustable stadium lights. The uniformity value mentioned above can be achieved by installing no less than 30 narrow beam stadium lights on each field angle pole. If using wide beam distribution stadium lights, the number of LED stadium lights used can be reduced, but the result will be glare to the audience. If the light strip lighting method is used on the stand canopy, the medium beam and narrow beam lamps are used to disperse the lighting effect will be much better.

3. Brightness and glare

The luminous intensity per unit projected area of the luminous body in a given direction is called the luminance of the luminous body in that direction. The role of a TV camera is somewhat similar to that of human vision. Both the camera and the human eye use the intensity of the perceptual lighting as the brightness. Therefore, the picture contrast and its background are the most important for picture quality.

Glare can cause a decrease in visual function. Therefore, the glare should be limited and measured. Various sports events have key locations, at which high-brightness light sources are strictly prohibited to cause glare in the athlete's field of vision. Which are the key locations for sports competitions? For spectators, the front part of the public area on the side of the stadium and behind the goal have the worst viewing conditions. When designing the projection direction of floodlights, these positions are used to assess the optimal glare control. Inferior locations, these points are key locations.

Four-corner cloth lamp installation method. The height of the light pole should ensure that the angle between the bottom row of Lamps on the light pole and the center of the court is not less than 20. . In order to reduce the glare to the athletes and spectators, this angle can be relaxed to 30. , But this way the investment of the pole will increase, and the ratio of vertical illuminance to horizontal illuminance will decrease. The light pole should be set at the midpoint of the sideline of the court and deflected outward to 5. , To ensure the vertical illumination of the athletes near the sideline. By increasing this angle, for athletes towards the bottom line, the glare is reduced and the vertical illuminance is increased at the same time. The limit of the increased angle depends on whether the stand canopy hinders the normal lighting of Lamps and whether it creates shadows in the court. At the same time, the light pole should be located at least 15 outwards from the midpoint of the goal. , To limit the glare of players in the goal area when corner kicks are taken.

The above two angle limit lines determine the position of the light pole, and the ideal light pole should be as close as possible to the extension of the diagonal of the court. In order to ensure that the entire stadium is illuminated, the angle between the bottom row of light poles and the corner of the stadium and the stadium is not more than 70. , So as to effectively determine the minimum distance from the light pole to the corner of the stadium.

Side lighting method. The installation requirements of LED stadium lights are not only suitable for multi-tower layout, but also suitable for light belt layout. Seen from the longitudinal axis of the court, the minimum value of α is 20. It is only suitable for training venues and low-level playing fields, where the glare control level is low. α is 25. At the same time, the glare control is better, and at the same time there is a higher vertical illuminance. Although the increase in α is conducive to controlling glare, the vertical illuminance component is reduced, and the investment in the pole or light strip lighting will be greatly increased. It is impossible to increase the stand canopy in order to increase the α angle. The elevation angle of the floodlight near the sideline is determined by β. If there is a proper ratio between horizontal illuminance and vertical illuminance, β should not be

Greater than 75. . If the lamps on the edge of the stand canopy do not have a suitable β angle, LED stadium lights can be installed under the canopy or other special methods can be adopted. Side lighting method.

The number of LED stadium lights for each stadium project is determined by the illuminance in the stadium. In the four-corner lighting method, the number of light poles is less than the number of lateral lighting, so the light enters the field of vision of athletes or spectators is also relatively small. On the other hand, the number of LED stadium lights for the four-corner cloth lights is more than the number of the side lights. From any point of the stadium, the sum of the light intensity of each pole floodlight of the square lights is higher than that of the side lights and lights. The light intensity of the pole or light strip lighting method should be large. Usually, the choice of lighting method and the accurate position of the light pole depend more on the cost or site conditions than the lighting factors.

The glare index GR (FlareRating)=10～90, GR=10 means that glare has almost no effect on people, and GR=90 means that glare is unbearable for people. At any position on the field, its GR=50 indicates that the glare is "just allowable".

Taking into account the dark background of the stadium, part of the light should be directed to the stands, and the lighting of the stands should also be paid attention to. In order to differentiate the TV picture during TV broadcast, the vertical illuminance of the stadium auditorium should not be less than 0.25 of the vertical illuminance of the venue. In this way, there is sufficient contrast between the sports field and the background, and this level of illuminance can be achieved by the overflow light of the field lighting.

The problem of glare can be solved as long as the contradiction between the requirements of the audience and the athletes is coordinated. Therefore, the design should consider the light distribution of the projector, the installation method, the height of the lamp, and other factors. This coordination work should be done by the designer.

4. The effect of shadows

The brightness contrast is strong, and there are shadows at the same time, which hinder the correct adjustment of the contrast of the TV camera, which will affect the quality of the TV picture. Too dark will also affect the degree of visual comfort. On the other hand, shadows are very important for TV broadcasts and viewers, especially when there is a fast-moving high-speed football game, if there is no shadow A spectator with a far ball cannot track the target.

Careful adjustment of the floodlights while avoiding the unfavorable factors that affect the lighting can result in better shadow effects.
 
 

5. Color correction

In most sports, color perception is very important. Of course, the color distortion caused by artificial lighting does not have the problem of color discrimination within an acceptable range. The two important differences in color characteristics are: color table-the color performance of the illuminated environment; color rendering-the characteristics of the light source that truly show the color of the object. The color rendering and color table of the light source are determined by the spectral energy distribution of the light emitted by it. The color appearance of the light source can be described by the correlated color temperature TK, which is mainly in the range of 2000-6000K. The lower the color temperature, the "warm" the color table of the light; the higher the color temperature, the "cold" the color table of the light. The color rendering index of the light source can be expressed by the color rendering index Ra. The theoretical maximum value of Ra is 100, which is equivalent to the color of the object under sunlight. The visual atmosphere of the environment is represented by Ra. The higher the Ra, the more pleasant the environment. Since sunlight changes throughout the day, the impact of sunlight should be limited to a minimum, and the corresponding color discrimination ability of the human eye will not have much problem. For an ideal picture, the camera is adjusted to the color state of the artificial lighting source installed. For high-definition HDTV broadcasting, the color rendering index Ra≥80, preferably 90.

Color correction is important for both viewers and color TV broadcasting services. TV cameras and color temperature can be adjusted in a wide range to use light sources with a color temperature of 3000 to 6000K for TV broadcasting. However, the stadium is an outdoor sports field. When the light source is selected, the color temperature of daylight is 5000～6000K. This may happen. The game starts in daylight and ends in cold light when the sun sets (usually "all-weather" This word to describe). In the setting sun and artificial dual light, the color temperature of daylight is required to be consistent with the color temperature of the artificial lighting source, so that the TV camera can continuously adjust, and smoothly transition from daylight to artificial lighting.

For the purpose of color television broadcasting, metal halide lamps have been rapidly developed in recent years. Due to their high operating temperature, high pressure and other conditions, this light source has a color temperature of 3000-6000K, which includes all requirements for color correction. It can fully meet the requirements of color TV broadcasting in outdoor sports venues, so it is widely used.

6. The influence of stroboscopic effect

When the metal halide lamp is used as the lighting of the sports field, the discontinuity of the arc determined by the main frequency of the AC power source may cause the stroboscopic effect. When designing, the stroboscopic effect should be limited to a minimum. Usually, the light source can be evenly connected to the different phases of the three-phase power supply, so that the illumination at any point on the site is the superposition of different light sources, so that the stroboscopic effect can be minimized .

Conclusion

We understand some attention issues of sports stadium lighting. In the current market, LED stadium lights are a cost-effective energy-saving solution. Through anti-glare technology, they can provide players and fans with a more comfortable and relaxing experience. Therefore, it is definitely worth buying LED stadium lights for your football, cricket, baseball fields and other sports fields and arenas, because they can be used for free for a long time without maintenance. Welcome to contact us to find a solution and evaluate the project cost.