Light measurement terms
Lumen is the unit of luminous flux. This describes the amount of light emitted in all directions by the LED lamp.
The more lumens an LED lamp has, the brighter it is. Lumen - the new watt!
Illuminance Lux (lx)
It describes how much light from the light source arrives on a certain surface. There are defined values and guidelines for this.
The lux output can be optimized by using a lens.
The required illuminance is regulated by the EN 12464 standard. The lux guide values are given depending on the area of application.
These can be summarized as follows:
Park & storage areas 75 lux
Storage rooms 100 - 200 lux
Construction sites 50 - 200 lux
Industry 200 - 500 lux
Repair & assembly work 500 lux
Read & write 500 lux
Fine work (painting, sanding, etc.) 750 - 1000 lux
Color temperature / light color Kelvin (K)
The Kelvin temperature scale is used to determine the light colors.
Warm white (<3'300 K) , is perceived as cozy and comfortable
Neutral white (3,300 to 5,300 K) creates a more businesslike atmosphere
Daylight white (> 5'300 K) , has an invigorating effect and enhances contrasts
Daylight white is also used specifically for work and industrial light. Good lighting helps reduce error rates and increases employee performance.
Light sources with the same color temperatures guarantee uniform illumination.
Neutral white to daylight white is also used specifically for work and industrial lighting. Good light helps to reduce error rates and increases performance.
Color rendering (Ra / CRI)
(CRI = Color Rendering Index) Provides information on how naturally colors are reproduced in the light of an LED lamp. The lower the value, the worse the color rendering. The light bulb with the highest possible color rendering index of Ra 100 serves as the basis.
- Ra values below 60 distort the color. Warning signs and signal colors are no longer used.
- Ra values ≥ 70 are suitable for outdoor applications
- Ra values ≥ 80 guarantee good to very good color rendering properties. Ideal for indoor applications,
as well as work light for painters, plasterers, upholsterers, carpenters, etc.
- Ra value = 95 indicates excellent color rendering. Ideal for painting, color adjustments and vehicle preparation
As the CRI value falls, so does the light output - which is often the case with inexpensive LEDs.
Lumens per watt (lm / W)
For lightbulbs, watt was a more or less sensible specification. The LED efficiency of lumens per watt is now many times higher. Watt describes the power consumption of the LED lamp. LED lamps require up to 85% less energy than incandescent lamps and therefore much less watts.
It therefore makes no sense to replace a halogen spotlight with an LED floodlight based only on the wattage. It is advisable to compare the lumens per watt. This says a lot more about the LED.
PS: To simplify things, the rough LED rule of thumb helps: Wattage x 10 = number of lumens
Asymmetrical spotlights (cones of light directed towards the front) guarantee efficient lighting.
The asymmetrical alignment directs the light away from the mounting point and in the direction where it is needed. This avoids unnecessary glare or scattered light, which also reduces light pollution.
(See floodlight FIELD LIGHT Asymmetrical )