Technical characteristics of LED
Not all LED technology is created equally, although this is not always immediately apparent to the everyday lighting customer. What might look similar at first glance can be completely different when you look at the underlying technical characteristics of the lights: binning, risk factors, thermal management and brightness degradation are all part of the LED DNA.
Colour temperature
The difference in colour temperature between LEDs can be measured with the MacAdam ellipses in Standard Deviation Colour Matching (SDCM), according to the CIE 1931 standard. This system is based on the human eye's ability to perceive colour differences, ranked on a scale of 0 to 10. Within 1 MacAdam ellipse, a colour difference is not perceptible to the human eye. From 1 to 3 ellipses, it is very difficult for the human eye to perceive a colour difference. Delta Light generally uses the 1 MacAdam step for mono colour LED chips, to guarantee the quality of the luminaires. Tunable white and softdim are ‘2 MacAdam step’.
Risk of eye damage
The European EN 62471 standard for photobiological safety describes a measurement method to determine whether a lamp or luminaire poses a risk of causing eye or skin damage. LED light contains almost no light from the ultraviolet or infrared spectrum and is therefore not hazardous to the skin. It does, however, produce a high peak in the blue spectrum which, when viewed in a bright light source for a long period of time, can lead to irreversible damage to the retina, otherwise known as the Blue Light Hazard.
Whether there is a real risk depends on various factors. The brightness of the LED, the colour temperature, but also the light distribution and the distance from the luminaire play an important role. When an LED is placed in a light fixture, it is behind a lens, reflector or light diffuser, which reduces the light intensity.
The EN 62471 standard classifies lamps and luminaires into four risk groups:
Risk group 0: No risk, even if the light source is in full view.
Risk group 1: Limited risk, no more than 10,000 seconds (approx. 3 hours) should be spent looking at the lamp. This is the risk group to which all Delta Light luminaires belong.
Risk group 2: A maximum of 100 seconds of direct exposure to the light is allowed.
Risk group 3: Up to 0.25 seconds of viewing is allowed. This is shorter than the natural viewing reflex of the eye.
Light sources in risk group 3 always require protective measures. For the other groups, this depends on how the light is being used. If a light source belongs to group 2 or 3, this must be indicated.
The life expectancy of LED
Conventional lights usually burn out before there’s a noticeable loss of light output. Since LEDs have greater longevity than incandescent and fluorescent lights, the light output decreases over time before the LED burns out. We can measure this degradation of light intensity by the L value (lumen level) and the operating time, expressed in hours. For example, L70 60,000h means that after 60,000 hours the light intensity is at least 70% of the original light intensity. For Entero, for example, we use L90, B10, 50,000h.