Why Glare is Important in the Stadium Lighting?

Why Glare is Important in the Stadium Lighting?

With the advancement of technology, the rise of green lighting and the increase in people's participation in sports, more environmentally friendly and energy efficient lighting is gradually appearing on people's horizons and stadium lighting is receiving more and more attention.

Football stadium lighting is a necessary facility for football stadiums. It plays a very important role in the daily use of football stadiums, such as training, matches and TV broadcasts. Professional lighting systems for football grounds are also becoming more and more of a concern for owners. It is no longer a random light pole, just install some lighting, and pay attention to horizontal illumination, vertical illumination, illumination uniformity, illumination gradient, glare limit, light source colour temperature, display colour, strobe effect and other professional issues, so sports lighting is not simply focused on illumination, but also consider the impact of glare brought by high brightness lamps, how to achieve the illumination requirements, reduce the impact of glare, to ensure that the illumination uniformity is a very important issue!

1. What is glare and how is it produced

Glare is a visual condition caused by the uneven distribution of light in the field of view, or the presence of extreme brightness contrasts in space or time, such that it causes visual discomfort and reduces the visibility of objects.

Glare is mainly caused by the angle between the position of the light source and the point of view. A light source with a high degree of luminance, which is reflected, or a strong contrast in luminance, will allow the production of glare.

2. The dangers of glare

The effect of glare on vision can be mainly divided into adaptive glare, maladaptive glare and disabling glare.

1). Adaptive glare refers to the loss of vision that occurs when a person goes from a dark place to a bright place and generally recovers after a short adaptation time.

2). Maladaptive glare refers to the visual discomfort caused by the presence of a high bright light source within the visual field due to inappropriate luminance distribution. If you are exposed to uncomfortable glare for a long time, it can cause visual fatigue, sore eyes, tearing and reduced vision.

3). Disabling glare refers to reduced visual function or temporary blindness caused by a glare source.

3. Prevention and control of glare

(1) reducing the power of the luminaire to avoid high levels of illumination as long as the lighting requirements can be met.

(2) The luminaire must be installed in a reasonable position to ensure the protective angle of the luminaire and to avoid direct glare into the human eye.

(3) Increase the brightness of the background of the light source by changing the surface brightness and reflection intensity of the luminaire, so that the overall difference in ambient brightness is reduced.

(4) The choice of materials should also avoid materials with high reflectivity.

(5) The top brightness can also be increased through semi-direct lighting, semi-indirect lighting, etc., so that the light is evenly distributed in the space.

In traditional football stadium lighting, metal halide lamps are mostly used, but due to the high glare energy of metal halide lamps, it can lead to players in the game, often in multiple angles and positions, only to see the dazzling light curtain, can not see the ball and can not react in time, after leaving the blinding light curtain, there will be a short visual pause exists, long visual recovery time.

Today, with the maturity of LED lamp technology, brand new sports lighting LED lamps are used to replace traditional metal halide lamps.

LED lamps have a clear advantage over metal halide lamps：

1). Metal halide lamps take more than 5 minutes to start, LED lamps light up immediately when the switch is turned on.

2). Most metal halide lamps have a colour rendering of 60Ra or less, LED lamps have a colour rendering of 80Ra or more.

3). LED lights without strobe.

4). The service life of LED lamps can be more than 50,000 hours, while the service life of metal halide lamps can be up to 10,000 hours.

5). LED lamps have good glare control; rich light distribution, which can meet the lighting needs of different venues.

6). Energy saving effect is obvious, with more than 60% energy saving than metal halide lamps.

7). Metal halide lamps have a high annual light decay rate.

8) . LED lamps are more likely to meet the requirements of television broadcasting.

General stadium lighting is graded according to the following form based on televised and functional requirements of use.

Grade	Functions Used	Televising requirements
Ⅰ	Training and Recreational Activities	No TV broadcast
Ⅱ	Amateur Competitions
Ⅲ	Professional Training
Ⅳ	TV broadcasts of national competitions, international competitions	TV broadcasts available
Ⅴ	TV coverage of major national competitions
Ⅵ	HDTV broadcasts major international matches

The index of glare values varies according to the use of the different scenes.

Glare index limits

Type of Venue	Indoor	Outdoor
Training and Recreation	≦35	≦55
Competition	≦30	≦50

Standard values for indoor venue lighting, like basketball courts, volleyball courts, indoor football pitches, badminton courts and table tennis courts should comply with the chart below.

Standard values for indoor venue lighting, like basketball courts, volleyball courts, indoor football pitches, badminton courts and table tennis courts should comply with the chart below.

Grade	Eh (Ix)	Eh		Evmai (1x)	Evmai		Evaux (1x)	Evaux		Ra	LED Rg	Tcp (K)	GR
		U1	U2		U1	U2		Ui	U2
I	300	-	0.3	-	-	-	-	-	-	65	-	4000	35
Ⅱ	500	0.4	0.6	=	-	=	-	-	-				30
Ⅲ	750	0.5	0.7	-	-	-	-	-	-
IV	-	0.5	0.7	1000	0.4	0.6	750	0.3	0.5	80	0	4000
V	-	0.6	0.8	1400	0.5	0.7	1000	0.3	0.5
VI	-	0.7	0.8	2000	0.6	0.7	1400	0.4	0.6	90	20	5500

The glare value in each class of court shall be GR ≤ 30, in accordance with the international standard for indoor courts.

Note: Symbols indicate

1. illuminance

   E - illuminance;

   Eh - horizontal illuminance;

   Ev - vertical illuminance;

   Emin - minimum illuminance;

   Emax - maximum illuminance;

   Eave - average illuminance;

   Evmai - vertical illuminance in the direction of the main camera;

   Evaux - vertical illuminance in the direction of the auxiliary camera. 2.

2. Uniformity

   U - uniformity of illuminance;

   U1 - the ratio of minimum illuminance to maximum illuminance;

   U2 - the ratio of minimum illuminance to average illuminance;

   Uh - horizontal illuminance uniformity;

   Uvmai - vertical illuminance uniformity in the direction of the main camera;

   Uvaux - vertical illuminance uniformity in the direction of the auxiliary camera;

   UG - uniformity gradient. 3.

3. colour parameters, glare index

   GR - glare index;

   Ra - general colour rendering index;

   R9 - colour rendering index of the light source for the 9th standard colour sample;

   Tc - colour temperature;

   Tcp - relevant colour temperature.

And for outdoor fields, such as football, hockey, baseball and softball fields, rugby fields, etc., the standard lighting values should be in accordance with the table below.

Grade	Eh (Ix)	Eh		Evmi (Ix)	Emai		Evaux (Ix)	Eaux		Ra	LED Rg	Tcp (K）	GR
		U	U2		U	U2		Ui	U2
I	200	-	0.3	-	-	-	-	-	-	65	-	4000	55
Ⅱ	500	-	0.5	-	-	-	-	-	-				50
Ⅲ	750	0.4	0.6	-	-	-	-	-	-
IV	-	0.5	0.7	1000	0.4	0.6	750	0.3	0.5	80	0	4000
V	-	0.6	0.8	1400	0.5	0.7	1000	0.3	0.5			5500
VI	-	0.7	0.8	2000	0.6	0.7	1400	0.4	0.6	90	20	5500

The glare value in each class of court should be GR≤50, in line with international standards for outdoor courts.

In a word, the glare value is very important and needs to be designed into the the sports lighting projects.

At last, in the lighting design of LED stadium lights at football fields, the following 5 points need to be considered.

(1) During the football match, in order to ensure the brightness of the light, to meet the visual requirements of the players and referees, there should not be glare, so as not to affect the players' game and affect the accurate judgment of the referee.

(2) To meet the visual requirements of the spectators, and the light should not interfere with and affect the game.

(3) To meet the lighting requirements of the relays, should have high colour rendering, no strobe, and improve the lighting effect as much as possible to make the relays of better quality.

(4) Lighting equipment must be installed and maintained at a later stage with due regard to its convenience and safety.

(5) Should give full consideration to energy saving issues, should choose energy efficient LED stadium lighting.

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