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Getting enough light on the ground without bothering the neighbours is a great start to a good game of evening football.  When evaluating what will, or won’t, work there is a number of parameters that will affect the results.  Lumens and Lux are 2 of the most common to be looked into so let’s explain a bit more about both terms and then the answer becomes more clear.

Lumens is a measurement of the volume of light being emitted by the lamp.  This is controlled by how the manufacturer of the LED chip (Cree, Lumiled etc.) has designed it and the value will vary depending on how much current is put through it.  For instance, a 5W chip operating at 5W may produce 90 lumens/watt.  That is, for every watt of power put in, it will generate 90 lumens out.  However, if you run the same LED at 3W you will get a big increase in the efficiency and generate perhaps 120 lumens/watt.  The lamp manufacturer therefore specifies a gross lumens value in two ways – raw lumens and effective lumens.  The raw lumens is what the LED manufacturer has put as the value at a given temperature and wattage.  This does not take into account the lamp as a system and doesn’t reflect any calculation for losses from optics, temperature etc.  The effective lumens is what is calculated once the lamp has been built into a system.  This is tested over a period of hours and so allows the lamp time to heat up and is testing the actual light output rather than the theoretical light produced in a laboratory by the LED itself.  If the lighting manufacturer doesn’t specify if the values stated are raw or effective, you can safely assume they are raw.  Losses from raw to effective may be as much as 30% and is specific to the system i.e. cannot be estimated without knowing more details about the lamp as a whole.

Lux, on the other hand is a practical, field measurement of real light on the ground or at a specified height.  This test can be done physically or simulated using software and the IES (digital light pattern) file. Once the lamps have been set up on their poles (or simulated) and the field is illuminated, then you can measure the actual light on the ground.  This takes into account the same losses as the effective lumens test but also shows how the light is controlled.  This is very important for big-field sports like football, cricket, baseball and rugby.  Having a huge mass of bright light that only shines 50m isn’t very helpful on a rugby field.  Additionally, the mass of light tends to have a lot of stray light which can tend to annoy spectators and neighbours.

So, whilst you have to have the right lumen values being emitted from the lamp, the way it is controlled is of utmost importance.  Just because a light has high power and lots of lumens doesn’t mean the light will go where you want it to go.  A proper lighting plan is therefore essential.  If you are not sure what lighting levels you need there are a number of sources of this info – a handy quick reference being is the Legacy guide but there are numerous more detailed sources available.  Once you know what the standard is, check out your lighting levels with a lux meter.  Again there are some helpful app downloads to give you an idea of where your illumination is up to.  If this is sufficient, use it as the base for your design.  If it isn’t sufficient, work with the lighting guidelines and the designer to come up with a system that works.

It’s a good idea to get a couple of lighting companies so you can compare the lighting plans from different manufacturers.  Once done you should be well on the way to making a better, more informed decision, achieving efficiency and low maintenance for many years to come.

 

Sport lighting is a specialised and complex science.  The lighting level, evenness, glare, CRI, heights and spill-light control are all aspects the designer has to take into account and all these parameters vary depending on the application.  For a game where the ball is small and fast moving, like tennis, high lighting levels are required with a very good CRI.  If the game is being videoed or televised the lighting levels and pitch uniformity have to be of a very high standard.

Over the years we have taken a lot of this for granted with metal halide systems.  Although an old technology, metal halide naturally produces a very high CRI, flicker-free light with a very good colour temperature. The development of the reflectors over the years has resulted in a very efficient system that was relatively simple for designers to specify.  With only two main beam patterns, almost any big-field sport was catered for and increasing the number of lights brought up the lux readings to the desired level.

The introduction of LED a decade ago was thought to signal the death of 2kW metal halide fittings as they are ‘old and outdated’.  However, while all other forms of lighting were changing rapidly, sport lighting remained surprisingly static. Early adopters burned their fingers with very heavy lights that gave bad light and failed regularly. As a result designers have shied away from these digital fittings that could potentially give them a bad name.  From our attempts, even as recently as 2015, it needed nearly 3000W of LED power to get a similar beam to a 2000W metal halide. Considering the extra weight and necessary pole thickness upgrade and the 100% increase in unit cost LED, was not looking very favourable.

However, LED manufacturers like Cree and LG have continued to improve light output and efficiencies. Optic designers have carried on working away and now there are some systems that can truly replace metal halide one for one.

However, when looking at doing a swap out there are a number of points to consider.

Weight and sail area (surface area)

The poles you currently use have been designed for a specific weight and sail area.  Increasing either, or both of these could have quite dramatic effects in high wind.  Make sure that neither of them exceeds what is currently used or obtain the original poles drawings to make sure the increase can be accommodated in the existing design.  This should be carried out by a qualified structural engineer.

Lux levels

Assess accurately what the current lux levels are of your field, decide what you need.  Just because you had it designed to 500 lux 20 years ago by no means guarantees that is what it is at present. Be realistic and don’t over-specify unless power consumption and capital budget are not an issue.

Power consumption

Once the layout design has been completed, ensure that the power consumption is within the tolerances of what you have available for peak demand. This might sound obvious but many systems have been implemented without taking this into account.

  • CRI requirement will depend on what level of sport is being played. For most training and club applications 70 CRI is sufficient.  If the games are to be televised or it is amateur level with a small ball i.e. cricket, then 90 CRI may be needed.  This is not something that can be changed later so needs consideration early on as the price is affected by up to 20%.
  • If you’re not sure about the company making the lights, or can’t find out much about them, the two most important parts of the light are the driver and the LED’s. Ask for make and model and research these thoroughly.  If both these components are from a reliable source, it is likely the lamp will stay the pace.
  • Some manufacturers have now used the metal halide beam patterns to model their LED optic. This makes is simpler for the designer so but essentially the beam pattern, uniformity etc should be dealt with by them (or the manufacturer if they offer this service) and you should be able to rely on them for this.

If you can satisfy all these requirements then, when added to the benefits of digital lighting, you will have made a good decision that will last a long time.