Variations in light and shade are a nuisance to both players and spectators, and thus require careful attention. The level of illuminance variation on the field is called uniformity. It’s expressed as a ratio of the lowest to the average illuminance. Increasing the uniformity value will help in optimizing the perception of the visual information used during sports events.:
- For football: in terms of uniformity, European norm gives minimum value from 0.5 (for recreational activities) to 0.7 (for top level competition). But it is always recommended to go above the minimum value to ensure better quality of illumination.
Glare rating (acceptable visual comfort):
Glare is the sensation produced by luminance within the visual field that’s considerably greater than the luminance to which the eyes are accustomed, and that therefore causes visual discomfort. For outdoor applications, CIE 112 defines a so-called Glare Rating factor (GR) for which an assessment scale of from 10 to 90 is given. The lower the GR value, the better the glare situation is. A value of 10 indicates unnoticeable glare and 90 indicates unbearable glare. Generally, a maximum GR value of 50 (just admissible) is specified for recreational sports.
- Make sure to install the right luminaire in the right place (and at the right height and angle). Once you’ve chosen the luminaire type and mounting height, the installation will be difficult to adjust, so make sure you take these issues into consideration well beforehand.
- Depending on the particularities of certain sports there are luminaire location restrictions, with the goal of maintaining comfort and limiting glare. An indoor basketball application should include no luminaires within a four-meter diameter of the hoop, for example.
As we all know, color rendering affects the quality of visibility in terms of how realistic colors look under artificial lighting, taking daylight as a reference. For training, European norms require only a CRI value of 20; for a match or game, there needs to be a CRI of about 60. (A CRI of 60 actually indicates average color rendering. Most new recreational sports lighting installations that use LED luminaires will today have a CRI of 70, which is higher than the EN norm stipulates. CRIs in the 80 to 90 range are observed mainly during televised sports events.)
This will depend on the recommendations you’re following. The European norm for a soccer field foresees a grid of around 21x13 points, whereas the French football federation foresees one of 5x5 points.
Maintenance factor (maintenance light level):
You’ll need to include this factor in your lighting calculation to compensate for light depreciation. Maintenance factor is defined as the ratio of the illuminance a lighting system produces after a certain period to the illuminance the system produced when new. Indeed, the quantity of light a system provides will decrease gradually throughout the life of the installation, mainly because of the lumen depreciation of the light source, dirt accumulation on the luminaires and the ageing of certain luminaire components.
Spill light control:
Carefully determine your lighting installation’s impact on the surrounding environment: roads, housing, and so on. You’ll also want to know at what hours (such as the night hours) spill light might be a problem for you.
Next, you define your lighting solution. Key solution parameters are:
Energetic efficiency (W/Lux/m²) and power consumption:
These are still very important factors to look at (in combination with others). If standalone LED-based luminaires can provide savings, combining luminaries with advanced lighting control systems like Interact Sports can boost savings even more – by leveraging dimming capabilities, for instance. The result is exactly the right quantity of light, where and when you need it.
Light distribution efficiency (utilization factor):
You also need to fine-tune the optic/luminaire so that it sends light only in the right direction. By selecting the right optic for the luminaire, you’ll be able to illuminate only the area of interest, giving you an efficient solution. This will let you avoid any light waste and shine light only where you need it. The utilization factor expresses the light distribution efficiency for a given playing field and given luminaire positions. (Defined as the proportion of the luminous flux emitted by the luminaire that reaches the field of play.) With a wide-range asymmetrical lighting distribution, OptiVision LED is a good solution for making a recreational sports installation as efficient as possible.
Quantity of luminaires and quantity and height of masts (relevant for outdoor use only):
- This can have a big impact on costs. How many luminaires do you need to meet your requirements?
- For an outdoor installation, you should define mast height so that you’re in line with the admissible glare rating. Increasing mast height will let you comfortably cover a larger area, but will cost more.
Restricting obtrusive light (relevant to outdoor use only):
Here you’ll want to consider how the recreational facility is going to affect its surroundings. The goal is to minimize light nuisance issues. You want to avoid beaming light:
- Towards the windows of houses
- In such a way as to discomfort people around the field of play
- Towards the sky (you need to mind the sky glow limitation, which protects night preservation and biodiversity)
Philips OptiVision LED with integrated louvers is a good solution for a playing field and its surroundings. It diminishes the light that shines beyond the field, preserving the darkness for local residents.