The column where you get to put your lighting questions to the Head of the Ovia Lighting business, Mike Collins, and his team of technical experts.
Q. MY CUSTOMER HAS COMPLAINED THAT THE COLOUR APPEARANCE OF LED FITTINGS HAS CHANGED OVER TIME. WHAT MIGHT HAVE CAUSED THIS?
Over time the luminosity of an LED lamp/luminaire will slowly decrease and will become dimmer. Although the technology for LEDs is very different to the old incandescent lamps, and they have a much longer life expectancy, it is a fact that LEDs will degrade over time.
An LED luminaire has a lifespan also known as lumen maintenance factor. For example our LED panels have an L70 rating at 50,000 hours. This is the most commonly used measure in the industry.
As a luminaire ages, its lumen output will depreciate, and we have to put a lifetime on it to fall in line with the IES standards. After the stated time the lumen output will have depreciated to 70% of its initial level. When it drops below 70% it is noticeable and will look a lot dimmer and maybe slightly different in colour due to the deterioration of some of the internal components on poorly designed luminaires.
The loss of brightness is mainly due to the structure of the LED. Impurities in the semiconductor crystal of the LED chip can cause material changes over time. This happens due to the LED being switched on and off, causing the LEDs ambient temperature to rise. If the LED isn’t able to sufficiently cool down, degradation will be accelerated.
I would say a good quality LED will have minimal degradation whereas with lower quality LEDs, as they degrade, it will be more noticeable to the eye.
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