Flicker is back with a vengeance, warns report

Around half of domestic and office LEDs have been found to have higher flicker rates than alternative sources, a report by the Society of Light and Lighting has revealed.

These sources imperceptibly or noticeably flicker more than alternative technologies. The SLL says this needs to be taken into account by designers, who should choose LEDs with lower flicker rates, or avoid using them in public places where they may contribute to adverse health symptoms in a very small number of those regularly exposed. However, buying expensive LED brands may not solve the problem: the researchers found that cost was shown to have no significant impact on flicker.

Those in procurement need to be very careful to include low flicker requirements in their specifications, and all specifiers need to be aware that if LED products are substituted by contractors or suppliers then flicker needs to be considered.

The SLL report also says that specifiers of LED lighting should similarly be wary of cool colour temperatures. ‘Other studies have shown that blue light can mimic daylight and confuse the brains of humans and animals into delaying melatonin production, potentially disrupting the sleep and the circadian cycle’. The report concludes that designers should therefore avoid LEDs with a high Correlated Colour Temperature (CCT). LEDs in streetlights should be diffused or recessed to reduce dazzle.

The report – on the topic of human responses to LED lighting and produced by Public Health England – concludes that the human reaction to light sources should be a primary factor in deciding to deploy them, not just efficiency or cost.

The report was intended to provide data on the positive and negative effects of exposure to light from LED light sources.

Researchers found that LED solutions are valid energy efficient options in comparison to other available light sources, with stated performance that is generally accurate in comparison, and that none of the LEDs tested presented a risk of retinal damage with proper use.

It also concluded that designers should consider the LED as part of the whole light fixture and the environment in which it is used to determine if it is suitable – a factor that is as important as the price of the LED or its efficiency.

‘There are still a lot of things to consider when deciding which LED lighting solution is best, and how to deliver it,’ says Society of Light and Lighting president elect Jeff Shaw

Cost was shown to have no significant impact on the flicker or colour rendering of the lamp, but there are potential issues surrounding LED lights which must be factored in when deciding where they should be used, and what kind of fixture is most appropriate for them.

Jeff Shaw, president-elect of the Society of Light and Lighting, told Lux Review: ‘This report is a valuable collection of data that will be extremely useful in enabling both the public and private sector to make informed choices when looking to procure LED lighting solutions and promote energy efficiency.

‘LED technology has advanced enormously in the last decade, but there are still a lot of things to consider when deciding which solution is best for you, and how to deliver it. What this report highlights is the need to consult a properly trained and qualified designer or engineer using the latest guidance to get the most out of an LED solution, and to ensure it is the best choice for people and the environment.’


  • Flicker is one of the subjects to be discussed at Lighting for Facility Managers conference, organised by Lux Review and taking place in London on Thursday 19 May. Places are free for FMs, energy managers and estate managers.