Lumen is listed on every datasheet, and it’s exactly the number you shouldn’t use to choose a luminaire. What actually reaches your site or field is lux, and in between are the beam angle, the mounting height, and the light loss from the luminaire itself.
This page explains the four key metrics, uses a calculation to show how many of the lumens actually reach the ground, and lists the five points to check when verifying a lumen rating in a datasheet.
Between those two lie the beam shape (candela), the distance to the surface, and the loss within the luminaire itself. With outdoor lighting, typically 40 to 55% of the emitted lumens land on the plane you intended to illuminate. The rest goes into the surroundings, and that is precisely where light pollution occurs.
All four measure something different, and the confusion costs money: a specification that demands lumens instead of lux cannot be checked upon delivery.
Lumens per watt, lm/W. The ratio between what comes out and what you pay for. This is the value upon which energy performance and payback period rest, and at the same time the value that is most frequently polished up on datasheets.
The DarkLicht series that we apply on sites and fields retrieves 172 lm/W net: measured on the complete luminaire, driver loss included. How to compare that number with that of another is explained below under the five checks.
The second is the inverse-square law: the illuminance at a point is the luminous intensity in that direction divided by the square of the distance. Double the pole height and you are left with a quarter of the lux at that same point. That is the reason why taller poles require more or stronger luminaires, and why a lumen specification without a mounting height means nothing.
A calculation example: a container terminal measuring 200 × 120 m that needs to reach 50 lux, using six 25 m masts and three 600 W luminaires per mast. That means eighteen luminaires, totaling 10.8 kW: on a terminal, that setup is more common than a single heavy luminaire per mast, because it allows you to distribute the beams across the site. The calculation can be verified, and the answer is the strongest technical argument we have.
An assumption: 4,000 burning hours with twilight switching and an open terrain without obstacles. On a large contiguous site, this percentage is higher than on a bounded area, because the beams from neighboring poles overlap on the usable surface rather than outside it. On a competition field of 100 × 64 m, the same calculation comes out to 62%, and for a larger field to 59%. In all three cases, it is the beam shape that does it: a flat-beam projector keeps the light on the surface instead of around it.
Two luminaires with the same lumens and the same wattage can differ by tens of percent in the field. The difference lies in the optics and in what ends up outside the field. You pay for that loss twice: in extra luminaires to meet the standard, and in light nuisance to the surroundings.
A full cut-off luminaire emits nothing above the horizontal by definition. Everything it emits therefore goes downward, and the only remaining question is how tightly it is kept on the surface.
When making a comparison, therefore, do not ask for lumens per luminaire, but for the lighting calculation including the number of light points, the lux levels on the site, and the uniformity. Then you are comparing installations instead of datasheets.
The DarkLicht M300 delivers 51,300 lumens and the Shark 50,000: almost the same luminous flux, two different tasks. You won't see that difference in the lumen figure, but you will in the lighting calculation.
Every datasheet lists the luminous flux, power, and photometric file we use for the calculation, which you can download without a form. For large zones from high masts, floodlights are the starting point, and what fits on a mast is stated on lighting poles and high mast lighting.
Lumens are not a lie, but it is a number with conditions. These five questions filter out most apples-to-oranges comparisons. If the answer is not there, that in itself is an answer.
Guideline values, not hard requirements: EN 12464-2 works with tasks and zones, not with a single number per site type. What your zone requires depends on the task being performed there and the traffic moving through it.
There is always a second requirement: uniformity. One hundred lux with dark patches in between is unusable, and on a sports field, it is grounds for rejection. And calculate using maintained values, not initial values: you agree on the maintenance factor in advance.
Chip efficacy versus system efficacy, and how net lm/W impacts the payback period.
What 3000, 4000, and 5700 K do outdoors, and where amber and dark sky belong.
How to read a lifespan statement, and why a number without an LB code means nothing.
All subjects together are on subsidy and knowledge base.
If your question is about your own site or field, a lighting calculation is faster than an explanation. We provide these free of charge, and you will receive a response from an engineer within one working day.
Lumen is the total amount of light emitted by a luminaire, in all directions. Lux is how much of that reaches a surface: one lux is one lumen per square meter. A thousand lumens distributed over one square meter gives 1,000 lux; the same thousand lumens over ten square meters gives 100 lux.
Lumen adds up all the light, regardless of direction. Candela measures luminous intensity in one specific direction, per solid angle: one candela is one lumen per steradian. Two luminaires with the same lumens can have completely different candela values, and therefore a very different beam.
Only if you know over which surface the light is distributed, and even then it is an estimate. Lux on an actual site depends on the beam shape, mounting height, tilt angle, reflections, and overlap between light points. That is what lighting calculations using the luminaire's photometric file are for.
Because what matters is how many of those lumens actually reach the area you want to illuminate. For outdoor lighting, 40 to 55% is typical; the rest is lost to the surroundings. A luminaire with fewer lumens but better optics can provide more lux on the target area and causes less glare along the path.
It works quadratically: E = I ÷ d². At the same point, doubling the distance results in a quarter of the lux. Yet mounting higher is often actually better, because the light then strikes the surface at a smaller angle: less tilting, less glare, and less disturbance to the surroundings.
The required illuminance in lux on the surface to be illuminated, with a uniformity requirement, as a maintained value, including the maintenance factor and the zone requirements for light pollution. Not a number of lumens per luminaire: that cannot be verified upon delivery.
Uniformity is the ratio between the lowest and the average light level. One hundred lux with dark holes in between is unusable: a ball or a forklift disappears into the shadow. In sports standards, uniformity is a separate requirement and grounds for rejection if it is not met.
Because every installation produces less light over the years due to aging and pollution. The standard requires that the level is also met at the end of the maintenance period. You agree on the maintenance factor for this in advance; that choice determines the number of luminaires.
That depends on the task, not the type of area: EN 12464-2 is based on tasks and zones. Roughly 5 to 10 lux for walkways, 20 lux for regular vehicle traffic, 50 lux for transshipment and container handling, 100 lux for detailed work, and 150 lux in a loading and unloading zone. Above 150 lux, the focus is on inspection and testing, and in those cases, color rendering is just as important as the illuminance level.
Send a floor plan or a sketch with the dimensions. You will receive a lighting calculation with the lux on the surface, the uniformity, the number of light points, and the wattage. Free of charge, and a response from an engineer within one working day.
